Not sure why you got downvoted, generally I agree with you regarding both the original racist "joke" and the reply in the second sub.

This one gets complicated for me, because as a base, I think racism is racism is racism, regardless of who does it to whom, or what their respective skin tones are. That being said, I think racism is slightly more understandable in some cases than others. For example, I think black Americans can easily look at incarceration rates between black and white Americans for the same crime, they can look at employment opportunities, they can look at funding for schools in predominantly black communities, they can look at policies like "stop-and-frisk", they can look at political representation and redistricting, and they have marginally-more of an excuse to be racist against white people than white people have to be racist against them.

At the end of the day, people need to reserve negative options for the irredeemable. For example, I can sympathize with the posters in the second thread, because white people have done, are doing, and will continue to do horrible things to black communities. However, I don't agree with them, because not all white people are irredeemable. Saying, "white people destroy everything they touch" doesn't help solve the core problems, though I can completely sympathize with the fatigue and frustration of dealing with this shit daily.

On the other hand, encountering a nazi, or klansman, or some Richard Spencer ethno-state motherfucker, they are irredeemable. They contribute nothing, they have nothing valuable to add to the conversation, they demonstrably make life worse for everyone except themselves, and in those cases it's perfectly fair to say, "I can't stand anyone that pushes a nazi ideology."

Edit: This has gotten a little rambly, trying to discuss both the original thread, and what I agree with from /u/braniac3397. What I agreed with in his statement is that freedom of speech is fine, but it needs to be applied in a responsible way. In general, I think anonymous speech (with very exceptions) is destructive to the intent of free speech. There are very specific cases where people in the modern world need anonymizing technology, in particular journalists in repressive regimes, and people organizing protests and specific actions against those regimes. I'm quite a fan of Oxblood Ruffin's work with the cDc/ Cult of the Dead Cow, as well as Hacktivismo, and think everyone should read and re-read his article on RadioFreeEurope RadioLiberty about the nature of hacking, hacktivism, and human rights: https://www.rferl.org/a/hacker_oxblood_ruffin_discusses_anonymous_and_the_future_of_hacktivism/24228166.html