But he still screwed up.
As you said, he shouldn't have facebook/twitter friends who are students (and apparently he linked the book there as well). The blog in question is reportedly linked on sites that students do use (if not his classroom site). His subject area would seem to overlap these technologies - so he should know better.
We both know that the reality isn't as important as the perception and how they can use it. He started a blog that clearly says it's for his students. If the blog had died out, he shouldn't have been posting things there (this assumes that the book is as they describe it... perhaps it isn't) or he should have re-designated the site for some other purpose (and not linked to it from sites students use). He can't make a legal defense that it isn't intended for students when he labeled it explicitly as that. He can make a rational/personal defense (as you do here)... but that relies on the the other side being willing to give him the benefit of the doubt.
He also really screwed up with the publication/copyright of student material without parental consent. I also seriously can't figure out why he would broadcast a recording that he wasn't allowed to make (and knew it). If he thought they were going to do something illegal (or that proved it was a witch hunt), I could understand it... but absent such damning evidence in his own defense, I don't see how he could be so dense as to hand them yet another bullet.
Having said all of that... to me the whole thing boils down to this: If the administration wanted to keep him, there's enough wiggle room and "explain-ability" to slap his wrist and keep him on staff. If they wanted to get rid of him... he gave them all of the ammunition they needed.
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