He's not THE top character anymore, if Peacemaker came out in the 70s when he was the undisputed top character they'd never allow those kind of jokes to be made about him. Also DC at one point wanted to rename the whole company Superman Comics so let's not act like he never got the star treatment Batman gets.
I see people saying Batman not being allowed to go down on Catwoman is somehow a sign of bias when NO male hero has ever been shown or said to do that to anyone. Can anyone remind me of a time Superman was said to have gone down on Lois Lane? Exactly, it's not a Batman thing it's a "we don't want our characters who we market to children in these situations" thing.
Whether anyone agrees with it or not WB clearly views DC as a family and kid friendly IP and think them doing something sexual, even if it's on an adult show, might hurt that image. It has nothing to do with Batman, they wouldn't let a B-lister like Green Arrow do it either.