These things never work for several reasons.
1. There are lots of liberal safe spaces out there to go to already like Reddit or Insta or Facebook and Dem Underground.
2. The rules they put in place inevitably make the site boring and just an echo chamber.
3. The people who go there want attention and to virtue signal. Inevitably that means you have to either A)Do even crazier stuff or B)Tear things down because it doesn't meet whatever standard you dream up.
4. After a while things play out and they realize that they are just sitting in a little room on a boat that is sinking and no one cares. Screaming in a room with a few other people gets old and people stop going, slowly at first and then suddenly.
5. Eventually whomever is behind the site realizes they are losing a ton of money and it's not getting better so they go out of business.
6. Not long after someone else comes up with the same idea and decides "This time it will work" like all good socialists.
"The most terrifying words in the English language are: I'm from the government and I'm here to help."
Ronald Reagan