Sorry to bother you, sir, but I just wanted to know: if I add a member to my trust list and, peradventure, the member on my list commits something bad that makes him de-trusted and red-tagged, will it affect my trust history in the forum?
I think you are confused here. If you add someone to your trust list, that should be because you think that person leaves good feedbacks and has a good trust list. In theory, if that person gets red tagged, should not change your perception of the ability to leave feedback that he has in many cases. Now, there are times when someone is massively red tagged as a scammer and then people stop trusting him in general, so they also exclude him from the trust list.
Remember they are two different things, and I'm going to bring you a quote from LoyceV here from a thread you might be interested in reading:
Don't confuse your Trust list with feedback
Trust feedback: leave feedback to people you trust or don't trust. Or leave neutral comments.
Trust list: a list of people who's judgement on others you trust (username) or don't trust (~username).
Also, if I give someone any feedback and, let's say, the person gets biased and is no longer worth the feedback, is it right to remove it? I just want to know, sir. Thanks.
Of course, you can delete the feedback or change a positive for a negative or neutral and vice versa.