I don't, but only so long as they don't ascribe magical or supernatural qualities to physical phenomena.
It's one thing to believe alien spacecraft as an extremely unlikely possibility, and another to consider it not only likely, but indisputably so. The lack of skepticism combined with unfalsifiable claims are what disqualify him, in my view.
There does seem to be a fringe of interesting events in the field worth studying. I'm not convinced that there aren't plausible explanations for them - after all, how many "black triangle" sightings are likely to have been classified stealth aircraft? But I also think the negativity serves a valuable purpose as long as it keeps people from entertaining flights of fancy.
I'll believe the Robert Bigelows and Bob Lazars and Whitley Streibers of the world when they can back their claims up with undeniable and irrefutable evidence. Given the nature of their claims, I don't believe that's an unreasonable bar to set. Even Einstein was doubted until someone proved him right.
But beyond that, I think we can agree that the conversation elsewhere in this thread demonstrates there is a whole lot of negative context which serves to drive people away from taking it seriously.