Their explicitly stated reason for withdrawing him is due to the controversy--this is a factual thing, that has nothing to do with guilt or innocence. At no point are they withdrawing him because he shot a kid, they are withdrawing him because he is at the center of a gigantic shitstorm they want no part of. If he is on campus, it will turn violent, and it is likely non-Zimmerman students on both sides will get hurt. THAT is what they are stated as trying to prevent. You can call them out for lying, but again their reasons for withdrawing him from courses have nothing to do with whether or not he is the criminal here or the victim of a media smear campaign. I don't even know if that's the official reason put down on the paperwork (my guess would be more that the controversy rendered him incapable of attending classes this term, so they're withdrawing him), but there is absolutely nothing about their statement that presumes his guilt or damages his eventual conviction.