Have you listened to the joe rogan episode where he talks about it?
It seems a little ridiculous to compare the one where he turned his engine off and on one time at night over a couple campers to the episode where multiple pilots see it, with multiple sensors seeing it from planes and from ships. He engaged in horseplay once, therefor anything he ever says should not be believed seems lame.
Given other potentially questionable behavior around this subject matter, yes, that absolutely calls their credibility into question.