I'm sorry but really? In any other Job you'd get fired for watching the Movie during working hours anyway.
This was dumb and immature. I have no problem with teachers showing Movies of any kind in class personally, as long as they have a significant value to a lesson being taught. And if it's in anyway a rated movie, maybe just inform the parents, saves everyone the hassle later.
I'd argue first offense, but I can't be sure of that really. And let's just grow up for minute, this is the real World, make a really stupid mistake and you get fired. There are other teachers willing to do a good Job, and not jerk around.
Sure if it's in any way controversial, that schouldn't apply. But this was just a plantant miss step due to poor judgment. If he'd thought about this just a second longer bevor showing the movie, he should have smelt this thing a mile away. And if he didn't see this thing coming, I wouldn't want him teaching my children anyway.