I'd be interested to know who you're talking about here. I don't dispute that this has happened, because in my time on the forum I've seen members kicked off DT for all sorts of shenanigans. Quickseller, Master-P, and TECSHARE are two that immediately come to mind, but there are more. aTriz wasn't on DT, but he was probably close to getting on it and he was a good campaign manager who ruined his reputation by not calling out a scam soon enough. I'm curious as to who you are referring to, however.
I got aTriz showing as being on DT2 (I temporarily disabled my custom list)
When you see the minus figure on the DT list it doesn't mean that they were previously positive. The (-2) just means that 2 members of DT1 have put an exclusion in place. That could just be a pre-emptive action to stop someone else adding them. AFAIK there is no historical record of who was on DT.