Likely because he became skeptical of what the word "bigot" is used for due to the lifelong twitter crusade some of his critics have gone through to paint him as one. He brought on the Dilbert guy and gave no ground on the topic of Trump, which was the only time he had an alt-right guest on his show.
That being said, him leaving patreon is disappointing. Though it might be a situation where he feels there are people with enough pull (reza or glen) to try to push a patreon boycott of his show, claiming his podcast can cause radicalization or somesuch, and he would rather avoid the politics of what constitutes "agreeable" content according to the money exchanger.
He tweeted out this video and his patreon still exists. I don't think he's going to leave patreon. Still, he probably should just set up a system where he can collect donations directly from his site.
Harris' main issue was the deletion of the accounts with no chance for appeal. He explicitly mentioned that he wasn't familiar with Southern, but he didn't need to be because it isn't relevant to his point. That, of course, won't stop what has already happened in this thread with people saying he's somehow aligned with her or her cause.
In the video in the OP, Conte mentions that not having an appeal process was a mistake and that more clarity was needed on the process overall. Whether it is Harris or any other content creator that relies on patreon, they need to feel secure in their finances.