Honestly juvenile obscenity marks people as less-than-likely for me to like or talk to. I mean if you really feel that its "unique" or makes you "cool" or whatever variety of that word, then you probably don't have a high maturity level to begin with. I mean I don't get down on people for it publicly, but I'm more likely to ignore folks who go out of their way to be obscene.
I'm not a prude, I just feel if you've not even a modicum of creativity to choose a handle that doesn't involve such, yeah... it does mark people in my first glance judgement as probably someone I won't associate with.
If its a temporary joke, or something that might change things for me though. Like I've done odd names back in the Quake days just for fun, but I was also younger and tossing out throwaway handles on different matches out of boredom.
Eventually I did stick to a non-obscene handle and never bothered to do it again. But I don't take people with obscene usernames seriously, nor do I listen to much, if at all, of what they have to say because in experience it generally is some kid (or adult who never matured) that is reminiscent of Xbox-Live chat. Basically a bunch of bullshit I mute in a heartbeat because its so juvenile and annoying.