Don't Debate Pornography

I'm hearing more and more Catholics, maybe I'm just becoming more aware of it saying you should never be engaging with people like this. You should just be soundly refuting them, but don't give them any kind of platform. It's a hard line to draw about what we debate because you're right. But are there topics you would refuse to debate? Like someone who is advocating for full on racism or pedophilia? Would you give them a platform? And if not, what's the difference?