How do we create an environment to foster diversity of thought?

Step 1. Instill in people the idea that just because they're offended doesn't mean they're right. And They're Right to Free Speech doesn't negate another's.

We need to get over our own pride, egos, and simply learn how to respect our fellow man again. Right now, we live in a world of hypocrisy. There are many who cry that we need to be more tolerant toward those of differing views, but they have no tolerance toward your views and consider you a bigot until you think like they do. In short, there are many trying to squelch diversity of thought and have us all in one mind; with the same morals, same ethics, same views toward thus group or that, etc. It's almost like it's a crime to simply "agree to disagree".
I think the most important thing is don't force it. Forcing people to think differently from their norm causes them to become defensive and resistant. Until respect each other beliefs and try to impose our will on others, we will have diversity of thought but it will not be a peaceful diversity. On a personal level, I tend to segregate myself from those who are different from me in many aspects. It's not because we disagree, it's because we can't disagree respectfully. This is happening on a grander scale as well as people are looking for "safe spaces" or other like behavior.

Or it's possible I misunderstood your question in which case this post is just gibberish. For that, I would apologize.

We will not have diversity of thought as long as the left is in control; they try to silence and discredit their opposition when they cannot compete in the marketplace of ideas. The intolerance for opposing ideas on our campuses today is the perfect illustration of this.