The look of the thong leotard over tights is kind-of old!  Several years ago, Dance France (A fitness-wear and dancewear manufacturer who I think has gone out of business.) featured it in their catalogues.  They also had guys in unitards who wore thongs over the unitard.

I started wearing trunks or briefs over my tights before that.  Whenever I wore grey or white tights with my dance group (a small company) and would sit around the studios waiting for my part, I'd get the butt dirty.  By wearing a black trunk, it kept my butt clean.  Everyone liked the look, cause the colors contrasted, so I continued to wear the trunks over tights.

When thong leotards became popular for women, I thought the look would look just as good on guys, so I started wearing thongs over tights.  Dance France made a great thong-backed trunk or brief that had a high waist.  I would wear those with an elastic belt, contrasting the colors.

In my experience some guys and some girls will freak-out when they see another guys butt-cheeks, be they covered in tights or whatever.  I've also found guys and girls who like the look.

To tell you the truth, I've had lots of guys from my ballet classes ask me how I get my tights to fit into my butt-cheeks, so the material fits down in the crack.  Once I was taking a dance class at a Univeristy, and in the locker room this wrestler kept staring at me, and would make remarks to his teammates. I really didn't care, but after a few weeks I went up and confronted him.  I started to be defensive, but he replied "How do you make your butt look so good in tights? I've tried to do the same thing, but it doesn't seem to work!"

In short, I wear whatever "look" I like and don't worry about.  Sure, some people will make comments, but they are entitled to their opinions.

balletboy

P.S. You didn't say if there was a "gay" issue here.  If you're concerned that you're straight and don't want the other guys to think you're gay, why do you care what they think?  You're not going to go to bed with them.  But that hot chick over there who likes your butt is what matters.  If you're concerned that gay guys may proposition you, just say "Thank you, but no."