Whether or not you would buy a bodybuilding shirt worn by Dave Fischer or not is up to you; but if you did buy one I don't think it would be "gay" in any sense...just like I dont think the guy who buys a "worn by Wayne Greztky" hockey jersey is gay.
As for Nasser's personality, here's my story:
When I first started working out in my late teens, this was before bodybuilders had websites and email addresses you could contact them on...they would have mailing addresses (usually their gyms) at the end of the their articles in Flex Magazine where you could write to. I wrote a letter, typical of a young person just starting to work out, and had questions like what kind of exercises should I do, sets, reps, etc. what do I eat, etc....and he wrote me back a lengthly handwritten letter and sent a free autographed 8 x 10. From there I knew he obviously cares about his fans more than most, but that's just the start. The first time I met him was THREE years after that letter, and we had no contact in between. He came to Muscle Beach in Edmonton for an autograph-signing session. When it was my turn, I told him my name for the autographed picture (first name only), and then mentioned in passing that we exchanged a letter long time ago. He paused and goes, "where did you write from?" I told him the name of the city, and then he said my last name back to me! Meaning he remembered my full name for three years with no contact. I found that amazing considering how many people he meets and how many people must have wrote him over the years. From there I knew Nasser was different than any other pro in the amount that he actually does care about his fans to remember details like that.