Paranoid schizos are often amazingly logical. Sometimes, you just gotta step back and say 'that's crazy talk, man!'
If you have any idea what you just said with those two contradictory sentences, perhaps you could find a way to say it in understandable terms.
In any case, just taking the first sentence by itself, it's of course true that someone could be babbling total illogic on one subject and be completely lucid on another. Sometimes people have strengths and weaknesses, sometimes uncontrollable emotional urges or bad dreams or whatever might get in the way of thinking rationally about a particular subject, or any number of other explanations.
All in all, however, it doesn't matter. If the initial facts be valid (and those can always be cross-checked), then all that's left is the logic in interpreting those facts. It doesn't matter whether it's Albert Einstein or Jeffrey Dahmer who's providing that interpretation. All that matters is whether the logic is sound. As a right-wing professor who's presumably practiced in critical thinking, you should know that, one would think.