So, I'm taking a look at Detective #431, and I see this:
Well, I don't know about that. Someone who thinks they might get unjustly accused by a masked vigilante might do those things. I'm just saying.
Let's keep going. This guy is really no physical threat to Bats, agreed? Thusly:
Yeah, that's pretty lame. Not that I'd want a lawn sprinkler upside my head, but this guy isn't exactly Bullseye.
So, once he's sure he can pound this guy at leisure, look at what a colossal tool Bruce becomes:
You eyeballin' me, boy? You want some of this? I don't think I like yer face!
Yeah, I'm kind of throwing a Mississippi accent in there. You were doing it, too. Don't act like you weren't.
Now before you look at the next panel, please note that the guy has basically given up. He's not taking an aggressive stance, he's not threatening anyone - he knows he's going to have his face pounded into pudding if he doesn't cool it, so he just stands there.
And gets assaulted by Batman:
Um, Bruce? Fight was clearly over! He was unarmed and just standing there! Seriously, what is that?
I guess as long as you aren't using a gun, beating on someone is perfectly okay.