Why tag everyone? There are still a few good people who follow the rules; nobody is a criminal until they are caught.
Then there's that. And it all comes down to how the trust system should be used. You really shouldn't just give negative trust to a bounty hunter simply because that's what they're doing on the forum. I get that they're spammers (not just on bitcointalk, as you pointed out), but red trust should be reserved for truly untrustworthy members.
So, how would you classify a bounty hunter who uses alts to cheat? And taking more than he should? If that isn't an untrustworthy character, I'm not sure what is.
What do you propose we do about bounty cheaters, BTW? Because you believe tagging them isn't doing any good.