I cant tell you what to do about the situation. Im not you, or in your location or going according to your locations rules for internet dating.

what I can tell you is that craigslist has shut down their internet dating / personnals section due to child abuse perpetrators, human trafficking, and people using their site to gain access to victims for sexual crimes.

my point is if he is caught in one of craigslist random "stings" that they and the police do now on craigslist your significant other can face major prison time for things like prostitution, and other crimes based on your locations laws and rules.

my suggestion if this was me I would just be polite and say... next time you visit craiglist you might want to log out because I dont want to be involved. then just casually mention you heard people are not supposed to be looking for dating and sex on craigslist, its now against the site rules and the police do "stings" there now because of dating/ sex crimes were happening on it.