I've talked about porn with my bosses and co-workers. It's not really a big deal.
Actually it sort of is. It sounds like you might be a problem.
You're imposing your personal conservative standards on others. What if I told you that you can't talk about rap music because it offends me? That'd be incredibly arrogant. I think the problem is you.
What if I told you that you can't talk about rap music because it offends me?
Do you mean ever, or do you just mean to you (or in a group conversation in which you are taking part)? Because the latter would be absolutely fine. You don't want to talk about that, no worries. I won't bring it up. What's the problem with that?
Not all issues are equal. Porn, in particular, has a lot of history of abuse of its participants and objectification of a large class of people.
Rap music is a genre. If you said "rap music that talks about running around murdering police officers", despite the fact that no police officers were murdered in the making of that song, it would probably also be offensive.
EDIT: then again circle jerks are more common in some places than others.