Leaving a red tag on someone just because you disagree with him is very wrong.
If they are objectively spreading false information
over and over again, then it is very much right.
To be case-specific: You have to be a complete nutjob to believe the flat-Earth bullshit; they are similar to the anti-vaxxers gang (although the latter causes much more collateral damage). On the other hand, you have to be a nutjob to willingly transact with a flat-Earth believer if you don't have to.
I think he is spreading false info. Here is his record on negative trust. Looks like there are over a hundred of us. If we are serious about cleaning up the forum I believe this should be looked into.