If you lock or delete a thread, "there was a complaint" should not be a sufficient justification. The complaint itself should always be evaluated.
Actually, I thought that was going along better than before. Once upon a time, long ago and far away
, it seemed the moderator just did it and no one knew why. Recently it seems there is always a comment to the public that it is (going off topic, violating a forum rule, etc.) Comments to the individual I don't know about. I hope they are explaining to the violator - hard to change a behavior if one isn't clearly shown the problem - but I don't see that as a public event.
So I agree that the complaint itself should be worked for a good outcome for all. Doing that isn't necessarily easy, though, and we are here at the invitation of the forum owners, who direct the admins, who direct the mods, etc.
Their wishes take priority, IMHO. If I don't like the outcome, I can vote with my feet. I did that on another forum a few years ago. I even did it here once, for a while. I heartily reccomend just leaving for a while
It helps me to examine why I am so passionate about something - a frequent sign that I am preaching about my attachments.