If this is in an intimate situation, you obviously feel uncomfortable and don't know him well enough to join in. Just tell him that kind of talk makes you cringe and you'd prefer him to talk to you normally. You have to know someone REALLY well for those types of conversations to work! ;0) If this boy is just saying these things to embarrass you, I wouldn't verbally respond at all. Just look him straight in the eye, shake your head slightly in a "what a moron" manner and turn your back on him. That usually sends them off feeling pretty silly.

Its sounds like you don't want him to...? tell him you're uncomfortable with him talking like that. tell him to stop. don't let ANYONE disrespect you like that!!

Ive just dumped a guy for this reason. Depending on how, where and when a man talks dirty to you. For instances such as my case. This man I met, within 10 mins of meeting me, talked dirty, asking me explicit things what I would only share with someone who Im comfortable with in the bedroom. At first it was the dirty talk, then along came the nagging for obscene pictures etc. It was obvious he held no respect for women or for the word "NO", he still pursued to nag and talk like it. If you're comfortable though, start with light talking like "I love when you kiss me like this " etc. but if you're not, tell him to pack it in, its disguising, creepy and really cheap and desperate sounding.