Unfortunately this is a feature of the internet - You are right to block if you are uncomfortable with messages - You are aware of privacy settings for your profile. (1) You can say only receive PMs from people you follow (2) Make your profile private
It's always the messages I get that they aren't horny and aren't seeking for x rated conversation so then I proceed and ask them what they'd want help with and then they go into pervertedness but trying to act dumb
Accidentally voted 'yes' but no, you're not the only one, I get that a lot. I don't block people for simply asking me questions about sexual stuff but as soon as I notice they're trying to turn the discussion into some kind of wank-material I tell them off and if that doesn't work and they simply won't stop annoying me I block them eventually. I didn't have to go that far too often yet though lol..