Much less commonly said, but still true, is that extraordinary claims require extraordinary trust. I do not trust the people saying these things. That I can not 100% guess their motivations for this is not particularly relevant. They have a long history of consistent and large lies. Failing to take that into account when they're making this sort of claim is foolishness.
In fact at this point they're really in a Catch-22... if they really do try to come out with "Yes! Aliens! Really!" then we have the question of, why then were you lying the up to this point then? Because if they are real you've been lying and lying and lying and lying beyond my capacity to express in a single sentence... why should I trust you now, then?
I mean, it isn't that hard to imagine how "alien threat!" will require us to, once again, give them more power. It's absolutely astonishing how no matter what the problem is, the solution is to give them more power.