Conspiracyist

The person who calls into question and discusses, based on the data at hand, the statements of repeatedly proven liars, examples: politicians, ministers, presidents, corporatists, bankers, clerics, scientists paid to falsify data (including doctors), journalists, magistrates, lawyers (well, no one has doubts about the latter).

In the old days they were called Heretics (from Coine, or Ancient Greek if you want, HERETIC, the person who brings infallible arguments that directly contradict the approved dogma or the approved political line)