Tin Foil Hat is a term used most commonly by people who are Conspiracy Deniers or haven't taken the time to actually research anything related to what they're talking about, and just assume that anyone that talks about conspiracy theories is wrong.
The term is most commonly asserted as quickly as possible in a conversation by the person opposed to conspiracies. Their attempt to belittle the conspiracy theorist by marginalizing who they are, is an extremely uneducated and ignorant way to attempt to argue their position, but the person using the term doesn't know any better because they believe that since most people see conspiracies as being wrong, that they will be praised for making fun of and/or mocking them.
Those who use the term Tin Foil Hat or its variations, are seldom ever capable of having a fact-based argument and have to resort to child-like tactics in order to (what is in their mind) prove a point.
Most commonly, California/West-coast trendies and Homosexuals are the main proprietors of using the term. The irony is thick seeing how the same social group has been engineered to call everyone that does agree with their political platform a "bigot," when in fact the meaning of the term bigot is being met any time someone uses the term Tin Foil Hat, irrefutably.