People responding to someone with "that's racist" isn't censorship. It's others exercising their free speech to strongly disagree with the points raised.

The end effect is the same, shutting down the conversation.

That just means it's a low value conversation. The end effect is very different. In my country there are anti-racism laws that /can/ put you in jail for saying something considered racist. Btw, I'm not totally against those laws. To say free speech has to be completely, 100% free, say /anything/ and any message you can think of, seems flawed to me.

Then come up with a better defense. The government is not preventing you.

How can you when the effect is to shut down the conversation?

Ok, and the difference between discussing it in the US is?