A long list of turn-offs!
Screw their negativity!
Turn off probably isn't the best way to put it. You aren't interested in every person you meet, as a romantic interest. Why? You have your reasons. All of us are attracted by certain things. We don't have to list what attracts us and doesn't attract us. We just know when we meet someone whether there is any attraction.
I recommend not writing someone off over a nose piercing though. Some of the most stable, established people I know have nostril piercings. If you're just looking for a sexual conquest, though, I suppose that if a nose piercing turns you off, then it matters.