Let's say that 100% of the servers were bastions of hatespeech. It seems like the folks in this thread would be against banning it in that case. But I think that's wrong. If the app was 100% just hatespeech sites, then it should probably be banned.
Now, then we get to reality: What is the real mixture? 80%? 50%? 20%? I don't have any background knowledge to make a guess. But I think it would not be difficult to show that whatever percentage it is, it would be far greater than say, what you can find on the average internet site.
Why do I say that? Because instead of going on Facebook, which is so easy that over a billion people use it... you have to pick up an obscure piece of software and run a server, or something. So the only people who are going to pick this up are likely technophiles, and people who have been banned from mainstream sites.