It means that a member of DT2+ has tagged you as "untrustworthy"/ a scammer / a fraud, you name it.
The user that gave it to you strongly believes that you are one of the above things, there's actually 3 things you can do against it, which are the following:
1. Convince the person that gave it to you to remove it, because you feel it has been given to you for an unfair reason.
2. Get multiple positive trusts from DT2+ members, correct me if i'm wrong, but i believe at some point this balances out the negative trust and it'll be neutral or again.
3. Convince members from DT1 to remove the person from DT2, so that his feedback becomes worthless, or convince DT ( Theymos) to remove the member from DT1, so that again, his feedback will become useless.
2 + 3 are unlikely to happen, so i'd say that talking to the person that gave it to you is probably your best option, in this case Vod.