Guys wearing singlets don't bother me, some people are more comfortable with their body than other I guess. I don't think you shouldn't wear a singlet if you feel you don't look tough or big enough! Do you really give a shit what other people think? I mean you are ther for you not anyone else. Just like when you are doing an excercise beside someone doing the same thing with twice as much weight, do you care about how you look doing less weight than him, or your form?
Guys that pose all the time and lean on equipment looking good, big or not, make me laugh to myself, I don't take it too seriuosly, not as far as wanting to beat them up!