PETA are interested in downright unreasonable goals. Even if they do not expressively go after meat, it's only because they realize how many supporters they would lose. However, given that there attitude is to treat every animal as having equal rights to humans, they have to be against meat, or else they are downright inconsistent in there views. One might argue that even if they are extremist, they will fail in there wilder goals, and still succeed in doing some good for animal rights. However, I cannot name a single force which makes people think more negatively of animal rights. Plenty of perfectly reasonable people interested in legitimately protecting animal rights have their capacity to do so greatly decreased because they become associated with PETA. For every 1 person who gently catches a fly and places it outside, there are 20 who don't boycott a puppy mill, or don't speak out against slaughterhouse conditions, because they are afraid that they will be lumped in with PETA. I know that I would speak out against, say, inhumane conditions in the meat industry, if it weren't for the fear of being associated with those nut jobs, and even when I do speak out against some form of animal cruelty, it's usually amidst a slew of people who would join me if they weren't too busy slamming PETA and being thankful that they lost another battle.
To put it another way: Ever notice how jokes about Seal Clubbing are a lot more acceptable in conversations related to PETA? That's because people know there crazy, and assume immediately that any position on the opposite side, away from PETA, is the right position to have.