Everyone is obviously in control of their own trust list and are able to tag at will, but if you do not have enough proof and are looking for opinions IMO best tohave a discussion in a thread and see what the community digs up before tagging.
What you stated above ought to be the standard but it may never happen. Every system has its weakness, and the few who spots this weakness uses it to guard themselves and as a tool against the vulnerable.
If I tell you that till this point I do not know how the DT voting works, you might be surprised. This is because I do not need the DT strength to fight anyone. All I want is a very sane community and not a community of gangs and lords.
If a DT member tags anyone for wrong reasons and refuses to reverse it, there is no way to remove the person from DT. I haven't seen. The best the victim will do is to ~ or leave a retaliatory tag.
If theymos for instance should create a poll to determine who leaves the DT, you will be shocked by the result of the poll.
If the system is failing, the consequence will be too many tags on people's profile and random ~ of users without reasons.