I think it really depends on your age. If you were a teenager dating someone six years younger, then it would be strange and people wouldn't accept it well. If you were in your 20s and dating a teenager, it would still be unacceptable (to some people). But if you are both in your late 20s-30s then I don't see a problem with it. Really, it's just how the world sees it. My boyfriend is 8 months younger than me, and some people say "How can you date someone younger than you?" but I don't care about it, because I don't see him as "younger" than me. I see him as "my boyfriend".