⭐ Merited by stoos (1)
It's not an abuse to give mass negative if it's a proven scammer, sometimes it's better to do so as the DT network is very dynamic now and the feedbacks can jump between trusted and untrusted after monthly DT1 updates by theymos.
I see and in case of scammers I totally agree. But beopen is not a scammer, he is respected member. It looks for me more that he is pursued by group of members, which were judging him earlier and still can not forget him, even if he was already painted and almost disapeared from the forum.
I totally agree, using alt accounts is not prohibited here nor lying about having an alt and this even doesn't deserves a negative tag.
The accusation made in the OP is even baseless as the campaign they were participating in did not have any such rules, and even if it had it was better handled by the manager of the campaign by kicking the participant out and not by some DT tags.
In our locale some users think that duplicating a review is some kind of wrong action. I mean, if you put someone on -1, that's enough. 
I think they are more concerned about your reason for the tags, as all of them are BS. As LoyceV said, adding alts to trust list is not an trust abuse.