I have been allowing neg trusted accounts into campaigns depending on the reason they have been tagged. With the New DT system we have, it's quite possible to see lots of users tagged by new DT users from the past who may not have revised their ratings yet. Also, some users just don't understand the trust system and do a lot of retaliatory tagging. Each person who applies with a tag will be reviewed regardless to see if they can still qualify for a campaign.
This is a very positive move. I do notice a lot of retaliatory tagging lately and with this new DT system anyone can be victim of an unfair tag.
However in my opinion, a user with red flag (type 2 and 3) should be avoided being in a bitcoin paid campaign.