If you're not offended by it, you have the option not so say anything. Depending on the situation, you might retroactively become associated with people who think the offensive thing is okay or good, but whatever.
People who say something (and on some things I'm one of "those people") have two things going on: 1 - they see the offensive thing, which is in and of itself offensive to them. But they also think "if I say nothing, then it's like I'm saying it's okay to say this offensive thing." And that thought, of consenting through silence, is offensive to them too. So now you have two layers going on. So you say something.
"Hey sorry, but my personal value system is wired to think this thing sucks AND saying nothing about it sucks." Then you get made fun of by people who think you have no right to get offended, AND also are annoying for saying something. Both levels of personal values get insulted in one fell swoop. But you say it again when it comes up again because you have your values, and you can't compromise about this shit.
Conversations evolve; threads aren't strict debate subjects. And really, talking about what's okay to talk about is generally what Dame's thread was about.