How do I explain to enlisted soldiers that most cadets do not attend basic training (without coming off as arrogant)?

BLUF: The Army has different training (and roles) for officers. Plain and simple. I didn't make the rules and neither did you. It's just the way it is. When my guys would question why the Army's reason for doing it "that way", I'd tell them to go get commissioned, work your way up to General or SECDEF or whatever position you need to be to change the rules, and then change them. Until then, shut up.

Having been a prior enlisted Marine before commissioning, I could commiserate with my platoon about basic training. In fact, I would argue that Marine boot camp is harder than Army Basic Training. At least comparing then to now. But they still brought up other differences. The LT isn't qualified on the 240, the LT never walks point, the LT never has to pull guard duty, etc. Well, officers and enlisted have different roles in the military. An officers main weapon is his platoon/company/etc. You don't have to be an expert on firing the M240, you have to be an expert on employing it and every other weapon in the platoon. And while doing that, you also get to keep up with where everyone is, if air support is on station, where the nearby friendly units are, does the QRF know your position, if you're on the correct route, if you're making the right time to the OBJ, and the list goes on and on. Officers have different roles. In some ways it's easier. In some ways it's harder. In most ways, it's different.

I don't see how it makes you arrogant that your training requirements are different from theirs. Either you did 4 years of training at a university/academy, or you did 13 weeks of misery at OCS. I've never understood why that should be so surprising. Just tell them the facts.

To be honest, ROTC is a bit of a joke. Just like everyone's Basic Training is different (location, cadre, instructors, weather, fellow soldiers, etc.), ROTC cadets also have different training, some locations and schools are more difficult than others, but in the main, it is far too easy and does not adequately prepare the Cadet to be an officer. That is why when young, inexperienced 2LT's show up, everyone rolls their eyes and the 'real' training begins. Just like ROTC, Basic and AIT training have been made easier and simpler so that the soldiers can be graduated and pushed through to enter into the system quickly and the expectation is that the units will train them to meet the standard. Sometimes it works, sometimes it doesn't. If a soldier has a bad attitude, learning difficulties, poor morals and ethics, those problems are passed along from basic to ait to the unit. As a future Officer, you have to recognize that the training is not as difficult as it should be, and that regardless of what is taught, it is not enough. You have to arrive as a 2LT in top physical condition, with a positive mental attitude, an open mind, willing to learn your new job, and listen to your senior NCO's and those that actually do the job (you may inherit an understaffed section that is effectively being led by a Corporal or SPC who is the subject matter expert). If you are in an Infantry Platoon, then you better know the systems you have to employ. Same goes for a maintenance platoon or a medical unit. Not having been to basic is a big disadvantage and ROTC summer camp does not make up for it. So you have to go the extra mile to learn your job and do it effectively without being dragged down by the system. Otherwise you will find yourself behind a desk all the time and you won't know the names of your soldiers (which occurs far too often). You have to downplay the weaknesses of the ROTC program and highlight the positive experiences, you are a 300 APFT Soldier, an Expert with rifle and pistol, driver, whatever. Basic is an introduction and an indoctrination. ROTC is (supposed to be) an introduction and a leadership school.