Yoda, you contradict yourself. You point out all these things that make it completely obvious, beyond a reasonable doubt, that it has to be the plants that caused the incident, yet you say M. Night doesn't like to be blunt in his symbolism.

If it really IS the plants, M. Night has lost all his subtle storytelling skills, because it's alluded to again and again and again in the movie that this is an environmental disaster and people are the problem.

So you can't have it either way. Either M. Night is subtle and there's something under the surface here, or he has bludgeoned us over the head with his political message. Either/or.
I don't think I've contradicted myself at all, because I didn't say that M. Night was subtle (your word). I said he doesn't like to say things outright, which is true. So in The Happening, he mentions a few theories, but doesn't technically designate one as correct. However, only one of them holds together upon closer examination.

I also didn't say it was "obvious beyond a reasonable doubt" (again, your words). And I then cited a number of reasons as to why I thought this was the case.

I'll gladly hear any counterpoints on these, by the way, but I don't think it's too debatable. The original script title, the fact that the characters base their decisions on the plant theory and we see things play out as if it were true, the decision to paint nuclear power plants into the background, the mention of nuclear power plants in the Northeast, followed by questions as to why the Northeast was the only area hit...all of these things make the explanation pretty obvious.