Funny question. I live in Spain where showing yourself of is part of tradition and I do appreciate seeing some good abs. Especially in the gym because that's the place where you can do this in a natural way.
I'd rather see guys doing that than women wearing these sportbra's and hotpants, showing themselves of ALL the time. Lifiting shirts is just part of being a guy in a gym here and at the beach they would walk up and down the shore to be seen and admired.
It doesn't bother me at all. It's a macho way of being in almost any Mediteranean country and I always appreciate a guy who takes care of his body by working out. I personally wouldn't lift my shirt or wear hardly anything to gym but I do go to the nude beach. That's more liberating to me than wearing few clothes to a gym.