One who believes in that line trusts neither, one imagines. The thing that people often misunderstand about not trusting something is that it is different from believing it is guaranteed to be wrong. Not trusting something means that it doesn't provide evidence. i.e. if you don't trust some source X, and X provides some evidence X_A about some event A then not trusting them means that P(A|X_A) ~= P(A) your prior probability.

People often interpret the "I don't trust X" statement to be "belief in the opposite", i.e. P(¬A|X_A) = 1. This is obviously stupid since someone you distrust could happily manufacture evidence for ¬A and then you'd conclude P(¬¬A|X_¬A) = 1 so they could make you believe anything, which is obviously not something you want someone you distrust to do to you.