Seems to me institutions like Acorn that accept the public as part of their operation can't really prosecute a whistleblower as a trespasser. I'm not sure what a pseudo-private area is.

What raynier is saying (I think) is that if it is illegal to trespass, then it is illegal to trespass for purposes of whistleblowing because that is still trespassing - imagine if they had trespassed, filmed, and found nothing illegal. If one of the farm workers were to film the video, there would have been no trespassing - it would constitute whistleblowing.