No, you got your points across just fine. But your points were not good ones. Here, let's go through this carefully.

Argumentum ad populum.

It was not an argumentum ad populum. Because I was making two points, neither of which had anything to do with the morality or immorality of offensive humor.

My first point was that if we remove all the comedy that offends someone, there wouldn't be anything left. So our choices are to a) censor everything that might offend anyone, or we need to put on our big girl panties and refrain from throwing a hissy fit when something offends us personally.

My second point was that the ubiquity of offensive humor tells us something about the nature of humor itself. i.e. That it functions as a pressure valve that releases tension around taboo topics. Offensive humor serves important social and psychological functions.

The fact that the majority of comedians and comics have made some sort of offensive joke, doesn't make it fine for them to do that.

Again, this was not my argument.

I'm not opposed to offensive jokes

No, you're just against those jokes that offend you personally, or that you personally dislike. As if your subjective whims are the ultimate standards by which society should police itself.

I just don't like when it's done in such a crude way made specifically to be offensive.

Right. So this is about your own likes and dislikes. Got it. The world should bend itself to your personal preferences. That's not narcissistic at all. By the way, how do you know the sign was made "specifically to be offensive?" Maybe it was made because, you know, the creator thought it was funny. Are you a mind reader?