It's unfortunate, but I think any new platform these days is going to have a toxicity problem. If a platform identifies itself as 'refuge' for 'freedom of speech', its first batch of users is going to be those who were unwelcome on existing platforms, due as much to bad behaviour as to point of view. I haven't signed up, but Parler seems to be walking a very fine line. To one side, they risk becoming the thing they tried to get away from, censored oppressively for corporate control. To the other side, they risk becoming a degenerate cesspool like Voat.
We, as a civilized society, might need to confront the idea that unabashed freedom of speech, as applied to internet platforms, might ultimately degrade into a toxic pit of hatred, circle-jerks and misinformation.:(