PETA’s advocacy of animal rights naturally involves criticism of people’s dietary choices, and that naturally makes some non-vegans to view PETA as an extremist organization. However, they are viewed a little differently within the animal rights movement. While their message is unapologetic, I actually think they are a relatively pragmatic and responsible organization - in addition to advocating veganism, they also campaign for issues that are agreed upon by many non-vegans as well as vegans, such as animals used for entertainment, experiments and clothing. Throughout the years, they have also been working with the meat industry in order to improve the welfare of animals used for food, and they have been criticized for this by some animal rights activists that view such pragmatic efforts as not radical enough and opposed to the idea of animal rights.
The whole extremist vs moderate distinction is obviously subjective and relative to the current mainstream ideology. Since the idea of animal rights is at odds with the current behavior of most people, I guess it’s natural that some people will view its proponents as extremists, even when they are pragmatic and reasonable.