Banning free speech extensions goes directly against what mozilla supposedly works for: https://www.mozilla.org/en-US/about/manifesto/
“We are committed to an internet that includes all the peoples of the earth”
“We are committed to an internet that elevates critical thinking, reasoned argument, shared knowledge, and verifiable facts.”
Dissenter specifically allows all the peoples of the earth to dispute facts on web pages that do not allow comments or where the page owner removes opinions that they do not agree with.
Good example: Twitter banning anyone/removing posts mentioning Tommy Robinson irregardless of the context or content.