I thought the way Mike took El hitting Angela with the roller was very in character because Mike idolizes El and has her on a pedestal. In S1, when El broke the bullies leg and arm, it was a life or death situation. She was like a hero. Then, in S4, even though Angela deserved it (lol), it wasn't a life or death situation and it's like seeing El do that crashed Mike's "superhero" image of El and what he thinks the morals of a superhero are...

CORRECT!!! this is exactly why mike had a problem with what el did to angela. the bottom line is: that isn't how superheroes act. they save people! and sure, they hurt people, but only when innocent people are in danger. mike saw el break out of his "superhero" idealization of her and simply couldn't agree with it.

also the way that when they're fighting he calls her eleven ("eleven, what is this? you're being ridiculous")... eleven is her superhero name! she just told him that she didn't want to be seen as just a superhero. she wants mike to love her for her. not for her powers. yet mike can't do that. he calls her eleven multiple times throughout the season, even though he was the one to give her the nickname "el." this was a clear dialogue choice used to link his superhero idealization with how he views (and speaks to).