This sounds to me like Mozilla could unilaterally terminate whichever user accounts from urlo and irlo, and there would be no appeal possible.
Not that I believe it is currently in Mozilla's interests to do so, mind you. But especially with the software world becoming more politicized and political winds in general being subject to change, it does not sound like a good idea to me to ask people to freely contribute, and have Mozilla then be able to just arbitrarily cut them off from contributions and connections made.
If this clause was included to have the ability to protect the community from clearly harmful people and/or behavior, that concern is quite valid. But so is the one I outlined above.