Thanks for the explanation, stealth. I agree with a lot of what you say. (By the way, here is the
actual ad.)
I don't think the affect on the meat industry matters, though. There are advertisements here in the US like "Beef, it's what's for dinner" and "Pork, the other white meat." This ad isn't much different. And like I said earlier, I don't consider a differing opinion to be harmful. "Don't use tobacco" and "don't use drugs" are acceptable advertisements, so I don't see why this one shouldn't be.
Your biggest beef (no pun intended) seems to be with the fact that this actress who is not an expert in the field is "preaching" stuff she knows nothing about. But isn't she just a celebrity spokesperson? They are used everywhere. In fact, this advertisement is really more of an ad for a website. Why should the use of a celebrity spokesperson be considered worse when the subject is about people trying to do the right thing rather than just pimping some random product? I would be more offended by a celebrity advertising a product that they know nothing about that was intended just to make money for that business. At least in this case she (likely) has more than just dollar signs in her eyes.
I know people generally don't like being preached to, but why is it necessary to look at it that way? I don't give a shit what Alicia Silverstone says about going vegetarian. I dismiss it because she is just a spokesperson. I also don't give a shit what Greg Norman says about Boeing, or what Sam Waterston says about TD Ameritrade. Why not just look at Silverstone's endorsement as being like the others?
I think that if you're angry about those who preach ethics and the right thing to do, especially in the case of this particular commercial, then you're putting your own filters on the message. Dismiss her opinion because you don't think it's based on anything substantive. Call her misguided for championing a cause that is only tangential to the real issue. Consider her an idiot for thinking that normal people can easily follow her lead. But why be angry that she's just putting her experience out there?