Why do some people feel the need to be openly antagonistic to Christians?

I think you need to notice that the atheists you hear about (dawkins, hitchens, etc) and the christians you hear about (huckabee, santorum, comfort) and the messages of theirs that you hear are all distorted by the media. But in person when you talk to people, try to get away from this ideas that beliefs have rights or that faith deserves respect. You as a person deserve respect. People have rights.
Beyond that, you've got no actual content or situations to discuss. You're just saying atheists are hostile to christians. As an atheist, I can tell you I'm never hostile to christians. I occasionally get into heated discussions about belief or politics, but in those cases, it's not hostility and it's just as likely that the christian started in on me first.
But I agree to respect you and avoid being hostile to christians. I just ask that you be a bit more specific if you've got an issue.

I wonder what you would think if another religion was proselytizing and evangelizing the way that some Christians do.

Evangelicals seem to think that they're under attack. Maybe it's their actions that cause that reaction.

Don't try to force your beliefs on others and stop politicizing your religion.

Even more so be a Christian in actions not just words.

Example?

I'll tell you why I speak up: religious people make policy everyday. And I think we could all benifit from a more secular nation. The libertarian in me suspects I'd feel this way christian or otherwise.

I usually don't like to bring up my faith at all. It is between me and God. I think others should adhere to that. I don't want to hear someone telling me how Christianity is so awesome. After that I will tell them something that doesn't confirm to what they think and all of a sudden I am the bad one. I have seen it far too much and too often. I think we would speak of faith both parties willingly do so. If not I don't care to converse of things at work or other places. That is just me.

Perhaps Christians are getting some bad PR?

I respect all beliefs, only I don't want to hear about it, and I don't want to talk about mine, unless we're having a religious discussion.

Well, why is it okay to be openly antagonistic toward Muslims? Why is it okay to say that those who aren't religious are anti-gun, anti-family, and immoral?
Outrage is only acceptable, it appears, if one feels that they are in the company of the majority.

As a practicing Catholic Christian, I daresay that the worst and most vicious antagonism I've received has been from supposed fellow Christians. I have a big-time problem with bigoted fundamentalist/born-again/Evangelical Christians telling me that because I'm a Catholic, I'm not a "real" Christian (never mind that my Church is about 2,000 years older than theirs), that my Church is the spiritual Babylon, and that the Pope is the Antichrist. With "friends" and supposed fellow Christians like these, who needs enemies? I'd much rather be in the company of atheists or agnostics than those insufferable dogmatic judgmental jerks any ol' day of the week.

1LT Nick Kidwell I would like you to consider one aspect of Christianity, indeed a command from Jesus Himself, and how that sets the stage for some of the treatment doled out by atheists toward Christians.

Jesus told his Apostles to go out into the world and spread the good news. Doesn't sound too bad, but... consider: that good news is this: God created the universe and everything in it. He is everywhere, is all-powerful, and He knows everything. God is perfect. God created you, but because the first man and woman He created thousands of years ago were beguiled by a talking snake (that God allowed into the Garden of Eden) into eating a piece of fruit that God told them not to, as soon as you were born, you were a sinner in God's eyes.

God is holy, and since sin is not holy, sinners cannot be with God. God tried giving the people law, but it was impossible for them to live by it and keep themselves free of sin. So because God loved us so much, He decided to impregnate a virgin, who would give birth to Him in human form. This person was Jesus. Jesus did a bunch of miracles to show he was the Son of God. He healed the sick, fed the multitudes, turned water into wine... but the people hated Jesus and they crucified him. They mocked him, ridiculed him, beat him, flogged him, they tortured him and then hung him on a cross for 3 days. Because he lived free of sin, his blood could wash clean everyone who believed in him and reconcile them to God. Now, because of Jesus' tremendous love and sacrifice, your sins can be washed away, and you can live in Heaven with Jesus and God and the Angels forever and ever.

So... an all-knowing, all-powerful being created us, allowed us to be beguiled, then punished not only the offenders, but every single human being that has lived since with a death sentence to an eternity of unspeakable agony and pain. This sentence was handed down to me the minute I drew my 1st breath, and unless I believe this story, ask Jesus' forgiveness and for Him to be my Lord and Savior, and get dunked in water, then I am going to burn in miserable agony for eternity, even though I'm only alive some 75-80 years, on average?

I'm sorry, but I do not appreciate being told that I deserve an eternity of unspeakable torture, or that the person who passed this judgment on me loves me, or that he sent his son to be tortured on my behalf, or that there was any real sacrifice (Jesus knew he would rise again, so...), or that this was a just action, or that it's ok for someone to punish the entire human race because a talking snake tricked a naive girl into eating an apple.

I have never simply offered that explanation to anyone. I have provided it though, after people decide that I NEED to hear their good news, or that I need to convert. No one says a damn thing to people proselytizing their Christian faith, but as soon as someone speaks out against it... Oh boy.

But Christians rarely see this as any kind of double-standard. Its perfectly acceptable to share the Christian good news. It just means you love people and are doing as your God commands, right? But what would the response be if I went to people and told them that religion was BS meant to control people? What if I went to someone's deathbed and did like Christians have done to atheists (You don't want to burn in hell, do you?), and lovingly told the person "Now come on, you don't really believe the talking snake, the burning bush, the Red Sea parted etc etc?" Christians get a pass, but you know damn good and well I wouldn't.

Like many things I tend to see social antagonism in political terms. All things are "a response to." As a Christian I see things in society that I put into groups (judgement). If it is bad (normative term), I see it as against what my religious beliefs are; or I see it as against social norms. If it is good, I see it as reinforcing social norms; or I see it as an example of the manifestation of my religious beliefs. Throughout my life what I perceive as good or bad has changed. This is mostly the result of what I would call the maturity of my faith.

There have been several things that have guided me in that faith. The first is who I am. Literally it is the meaning of my name "God is my judge." With that I recall several bible passages: Judge not, that you not be judged; If you have something against your brother you have killed him; You shall not kill; If it is of God nothing you will do will stop it, if it is not of God it will not last. I did not come by my faith because of what someone else did or said. I came to it by experience, when I was alone. For this reason I do not like to preach my faith but to live it. Yet there it is. Mostly it is for those who believe yet attribute social norms with religious requirements. My God has one requirement of me. To love.