In the absence of global, and with you having to rely on the leader of the clan to be truthful with you, it is clear you were deceived. If you had tried to find information, perhaps you would have realized what was really going on, but that is in the past now.
It appears that you have been in an FWA clan with zero problems for a good while, now that you understand the situation with sync stalking clans. Your former clan will surely continue to try to recruit you back to help them; don’t do it! They are banned and they want you banned too.
May I also suggest you remove all ways for them to contact you as well, since this will be a source of aggravation for a long time.
I vote to remove the ban from this players accounts. All of them