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 speech! 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.
I was loooking for these information which campaign. BESTCHANGE!! One of the high paying campaign. But its definitely one of the abuse that the participants are doing actually. It may not be a violation to some campaigns but bestchjange are looking to advertise. Post on mega threads I guess will not be seen by users as matter of fact there are less users reading those replies. Bestchange I guess have learned and still trying to find ways to make use of their spending.