Quick question...

Ok, I've been getting quite a few new friend requests recently. A lot of them I'm more than happy to accept, but some less so. It's easy to decline the ones that are completely empty profiles with nothing but a downloaded avatar and maybe one or two comments, but how about the ones that actually have a person behind them? Is it socially acceptable to just bump a request that doesn't appeal or that I have nothing in common with, or is it more polite to leave a comment on their profile explaining myself?
Thank you, people of xhamster! xx
-S