What exactly is the opposite of tagging scammers? Is it, being tagged by scammers?
Who knows. The problem with people getting on DT by way of scam-busting is that it doesn't really prove how honest that person is, and even though that is (I think) the reason I was put on DT, I still believe that. A member can easily just tag a lot of scammy accounts and work their way up to DT in order to pull off a really big scam. I don't know if that has actually been done, but it's possible. At least if you have a history of transactions involving money you could have scammed, there's some real basis for trust.
Depends on how they are getting into DT. If they are only echoing other users negative feedback and are doing no own digging, I would consider them not worthy of being DT. It's somehow a "proof a work" if someone is spending much time for his reports about scams (such like ICOEthics for example).
It would be easier for scammers to get into DT (or at least to receive some positive feedbacks) by just making deals with highly trusted DT members. That would be a fast and low-risk method if they go always first, receive a few green ratings and finally pull their exit-scam when someone else has to go first. Similar to the marcotheminer issue where also trust was tried to build by trading.
Scammers would most likely choose part two (trading) for their scams because part one (scammer research) takes too much time and effort.