We are not claiming here that forecasts must be perfect. This is effectively what you are saying, right?

No.  Wrong again. 


In fact, we are accusing him of fraud.


No you're not.  You are trying to defend a position.  If you were accusing him of fraud you would actually do that - accuse him personally and professionally of fraud and take legal action.  Do it formally.  Confront him with a legal filing or public article in the newspaper.  Why not do that?  Because you know he'd eat you alive.  You are not credible. 

Take him to court.  Here is how the proceedings would go:

Judge:  You are accusing M.A. of fraud.
You:  Yes your honor
Judge: Did your read the terms and conditions on the site?
You:  Yes your honor
Judge:  Case dismissed.  Pay M.A.'s atty fees for filing a frivolous lawsuit.