Scott was absolutely fucking wrong throwing Isaac around. Isaac is an abuse victim, Scott knows that. Isaac asked Scott to hit him, because he is an abuse victim, he thinks he deserves to be hit when he does something he considers bad. But it was not out of character for Scott to do that.
If this was normal Scott from last season, then yes that would be extremely OOC, but it’s not. Scott, Stiles, and Allison are all extremely fucked up this season because of the ritual they performed. They’re all OOC because what is going in inside their minds. They are not behaving like themselves. The title of this season is Lose Your Mind for a reason, they’re all literally losing their minds and losing themselves.
Allison’s trademark is her ability to defend herself, her archery skills, and she’s losing them. She’s losing a huge part of what makes Allison, Allison. Stiles is the researcher of the group, and he’s losing his ability to read. He can’t research without being able to read, he’s losing a big part of who he is and how he fits into the pack. And Scott’s trademark is his amazing self control and selfless attitude. He can’t control his transformations. He is losing the ability to control himself, and one of the side effects of this is the way he is treating Isaac. Normally Scott would never lay his hands on Isaac, ever. But Scott is not himself. If he was himself then yes, it would be extremely OOC and I’d be wondering what the fuck Jeff Davis was thinking, but that’s not the case. Jeff Davis knows exactly what he’s doing. He’s trying to demonstrate that they’re all losing themselves, and are becoming unable to do things that make them the people that they are.
Scott is not OOC because his character this season is losing himself. And when you lose yourself, you do things that you wouldn’t usually do. That is not bad characterization or bad writing, that is completely normal.
Does that make it right? NO. Scott needs to realize what he’s doing and he needs to work to control himself better. He needs to figure out how to gain back his self control and become the person he usually is.