You do once it's factually established that what they're saying is fraudulent, if they keep doing it.
Internet forums like this will have minimal impact on changing minds, so posts pointing to "proof" or "evidence" of one view or another are typically ignored or overlooked, because there is no one physically in the same space forcing an objective study of said proof/evidence.
While the knowledge/facts are out there on the Net, it takes real wisdom to be able to distinguish Truth from fraud.
Kinda like getting rid of Obama - it needs the tide of public opinion to reverse course - a complete paradigm shift.