No, I think the poll is entirely meaningful. I just think that it answers a different question than it purports to. Moreover, I think the question that it answers might be more inetresting. It's not telling us the sexual reality of PMB denizens, but rather the perception. Ultimately, I think the perception of what a sex life might look like without prostitution could be more interesting.
Actually, I suppose the most interesting thing would be having both results.
(By the way, 'effect' ecompasses skew direction, no?)