I can't agree with you. Open-source communities have both the right and the responsibility to protect themselves from toxic people. If I showed up in, say, the Firefox issue tracker and started trolling people and insulting their contributors, they'd ban me without thinking twice. I wouldn't have broken any laws, but they'd still be well within their rights to get rid of me.

Criminal law uses the "beyond all reasonable doubt" burden of proof.

Civil law uses the "balance of probabilities" burden of proof.

A project kicking out a member doesn't have to meet any burden of proof, they just have to show that they're not being discriminatory.