The wonderful thing about people is that everyone is unique. People express ideas and beliefs and it is their "right" to do so. If you don't agree, that is fine. However, trying to coerce another into your views isn't "right." I do believe there should be some restrictions to what is considered "expression," in order to prevent expoitation and other such things, though if the game is rated 'M' (or AO) then that's as far as it needs to be taken. Don't ban it simply because you don't agree with it - just don't buy it and if you like, write a piece about why you don't like it/don't think it should be purchased. Maybe through your "right" to expression of dislike you can reach some others.
(there are some issues with this post such as "rights" - not everyone has them and those that do often take them for granted, blah blah blah, but you get the point)