I see absolutely nothing wrong with the quote you got all defensive about:
some PA's are scary. Or perhaps I should say that it's sometimes scary the leeway that attendings give their PA's. For having only two years of post-graduate school/training, they are sure allowed to do a lot.
This is one person's opinion based on one person's experience. The fact is, this opinion and experience is not rare because the fact is that some attendings do give too much autonomy to PA's (according to accepted standards of practice and you know...the law).
Unless your contention is that PA's should be able to do whatever they want, you can't argue this point. There is a line that shouldn't be crossed, and some people cross it. That's not good. PA's are fantastic resources in the appropriate capacity, and potentially dangerous/scary beyond that capacity.
Edit: on a related note, is anyone else sick of midlevels on SDN getting all huffy and defensive any time someone suggests they're in any way less than a doctor? They do this constantly - someone says something pretty harmless (and pretty true) like the above quote, and some PA or NP or whatever comes in and gets all defensive...saying simultaneously making a big scene about how they KNOW they aren't a doctor but then extol how thin the line is between them and a doctor and how they're so super competent at pretty much everything.
Look at the posts above, and look at a LOT of the posts from medical students - everyone saying "listen, as a medical student/resident you have to know your place and don't get too big for your britches" and guess what? We all agree - as medical students/residents we are inferior to attendings and should know our place. Everyone's on board. There's a team, there's a hierarchy, there's a training and experience difference, and we respect that. But suggest to a midlevel that they should "know their place" and all of a sudden you're an elitist arrogant jerk. We should all know our place, and that means being honest about where the line is. The quote you got all defensive about is an example of someone (attending & PA alike) violating that line.