For this moment, we absolutely know there is at least a strong genetic component to autism, so if it stems from the environment, that claim of a supposed 'sole cause' is not going to be correct no matter what. For the other, there have got to be a hundred correlations that have been studied, each pointing in a hundred different directions. (For instance, men, did you know that your preference in women's curvature could cause your child to be autistic? That's the way the media presented a study...)
There's only so many "we've found the one true cause!"s that one can take before becoming a bit skeptical about the whole matter. I generally wait for there to be a systematic review, or something close to it, before starting to take a proposed 'cause' more seriously. I would recommend others do the same.
Edited to add: Read this article, and then you won't wonder why I'm skeptical when a new 'autism cause' is announced. The author (Emily Willingham, who rocks) put together a list of a lot of the claims that have been linked to autism. As you might imagine, there are a lot of them (I lost count), but Willingham has a sense of humor about them. There is a lot of sarcasm in here (and some mild salty language), this is NOT intended to be taken as evidence supporting any of these claims, simply to show the sheer number of them and, quite the opposite, highlight how ludicrous some of them are. As the claim about refrigerator moms should point out...