OP is referring to bestchange's signature campaign.
They removed few members because of posting on spam megathreads. According to the CM, any thread with more than 5 pages of replies is a spam megathread and some participants do not agree with this.

Honestly, I don't see what this have to do with freedom of speach! And if we are going to talk about rights, then they are within their rights to remove any participant who doesn't meet their standards.