Putting your content out there for all to see is without censorship is a fundamental part of Steemit. The addition of a 'block button' would probably be the first stepping stone towards another Facebook type platform. I'd suggest using the mute option and live with it. Creeps and pricks go hand in hand with posting paid risqué photos of yourself to a public blockchain. It wouldn't be fair to other users if their voices were silence on other topics because of the specific type of content you post. Good luck!