Flash was always just kind of a dick. He didn't go around torturing people and beating them up--he wasn't a violent maniac. In the old days the worst he did was hit Peter intentionally with a football. That's why when Flash and Peter become friends later it makes sense. It doesn't make any sense in this movie because he's depicted as an over-the-top dangerous psycho. That's why it doesn't make sense when Ben admonishes him for humiliating Flash, since this version of Flash Thompson is clearly a dangerous person.
What's that even mean?Honestly, this movie made me give a damn about Spiderman. THIS is how a kid who grew up with out his birth parents acts.