If they were trusted and they lost their credibility -just if that' s the case- then, what happens with the trust they give to others?? Sorry, my brain is just exploding here. 
Actually, you're making a good point here and I'm thinking red trust given by particular DT member, should be removed (Not other members given) if that DT member lost their credibility. b) Even DT member lost it credibility and accusation is proved but it does not mean that user lied earlier in every occasion. User feedback should remain there.
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Untrusted -ve feedback are also important while making a deal. Might be DT did not find enough evidence to tag or the scam accusation did not get attention of DT.
I think you didn't read my first post and read the bolded part 
While I'm agreeing with your statement, I am seeing another view regarding that issue. Because I'm not taking any consideration of the trust score when I reading posts, member suggestions, answers for questions(but not in trading discussions). So isn't that mean we are pre assuming, if we allowed to show trust rating in every boards people will judge their decisions by blindly looking only at the trust rating? No I'm not that catagory and I don't care that members trust rating when I'm reading, if he/she adding value to the ongoing discussion.
I think you choose the decontextualized way of debating. We all know what "theymos" said about the trust system. I am talking about when giving away your merits, we don't need to consider the red trust of that user.
(theymos didn't say anything about trust )
)Read the whole post "https://bitcointalk.org/index.php?topic=211858.msg2221664#msg2221664" here.
This is what theymos said about giving away your Merits (theymos didn't say anything about trust
)While we will not be directly moderating this, I encourage people to give merit to posts that are objectively high-quality, not just posts that you agree with.