Unless you're never going to park your bike somewhere that a family with kids will see it I would tend to think your new part is kind of over the line, but that's just my opinion. If I saw that on a bike I'd automatically think the owner was an a$$hole.
Same goes for those "nuts" hanging off the back of bikes and trucks and .......
Definatly not something I would EVER put on my bike. Two things I can say I've never done-swear in front of my mother and swear in front of my daughter. It might not seem like a big deal to most, but i'm proud f it. And seeing as both of them will see the bike, It wouldn't be for me.
I think "***** YOU" would have been a better statement, and maybe got a few chuckles to boot. I use the "F" word everyday, in closed company, but as a part of my bike....... even to dis-tasteful for me. But, it's your bike.