The tool might be used for extremism, in the same sense that ffmpeg, email, and HTTP are. That is not the same as saying most users of PeerTube will be inundated with extremism though.

Wouldn't having all speech be controlled by giant platforms be batshit?

It isn't anyone's job to rescue Parler. They're locked into a cloud provider, and that was their own doing. If they can't survive, tough kitty.

However, an open internet, with the ability to run apps outside of app stores (needed for new peer to peer stuff to thrive), and use of crypto would mean someone could make a Parler. Mastodon and Matrix have had major controversies.

Your local community library is also full of extremism. You will find copies of The Communist Manifesto, Mein Kamph, The Turner Diaries, The Anarchist Cookbook, Platos Republic, In Defense of Selfishness and The Koran.

It has “problematic” works like Huckleberry Finn, Satanic Diaries and To Kill a Mockingbird.

It has works written by known racists such as HP Lovecraft, TS Elliot, Roald Dahl, Dr Seuss and Kingsley Amis.

It has hard copies of dangerous films that have been memoyholed by Prime and Netflix like Gone With The Wind and The Jazz Singer. It may also have DVDs that have been produced, directed and acted in by vile, cancelled individuals like Kevin Spacey, Louise CK, Harvey Weinstein, or Mel Gibson.

Good God, it might even have a copy of the Jenna in blackface episode from the third season of 30 Rock. I am clutching my pearls and getting the vapors just thinking about it.

Probably, that's OK, because while there's no central platform authority there's also no barrier to anti-extremists using disruptive tactics against it.