If Theymos allowed me (or DT members in general) to start negging these morons into oblivion, I'd be spending hours each day doing it. Unfortunately, that wouldn't do much good for 1xbit's collection of shitposters, since the one OP pointed out (og kush420) has lots of red trust, and not even for his posting. There's a
tag from Vod from a few years ago involving an actual scam by that user, and obviously 1xbit doesn't give a shit about who's advertising for them.
It might help with shitposters in other campaigns/bounties, though. But it's still not a good use of the trust system, hence why people stopped doing it.
As you have already concluded, red tags are not something that would prevent such members from doing the same things they are still doing today. If you are already ready to spend the whole day leaving red tags in their profiles, it would be much more useful to use the
"report to moderator" option and hit them where it hurts the most, in the number of deleted posts.
I kicked out several shitposters from the Bitcoin discussion that way, they simply realized that it is not worth it for them to write posts that will be deleted.