Quote from WyttenbachI strictly adhere to mathematical logic: If somebody says Rossi is a crock/fraudster, then IH (and as a consequence, to some extent, - their supporters..) are crooks/fraudsters too, because only crooks/fraudsters openly deal with crooks/fraudsters.
Which is where your logic fails to model the real world. Rossi is not (publicly) known to be a crook/fraudster other than from the famous email. These things are not fixed and known true or false. Are you saying they should not have had any dealings with him because that email? Rossi has said weird things for a long time, it has not stopped anybody else.
In any case, again in the real world, there are many reasons why an honest man might need to deal with a crook, like it or not. For example, if he had a world-saving invention.