His views may be extreme, but they are extremely well thought out, well justified, and well argued (as long as you don't count user-friendly presentation and being nice to people as necessary requirements for arguing well). He's not wrong about what he says and believes, and he's extremely consistent about that, but his priorities are a lot different than most people's. And the world's a better place because of his influence on many less extreme people with different priorities. Plus he has a great sense of humor, if you don't let him get under your skin: http://www.art.net/~hopkins/Don/text/rms-vs-doctor.html
How precisely are his views extreme? The criticism of Stallmans opinions (as opposed to his behaviour which is another issue) I have seen unfortunately boil down to the fact that people can not even imagine sacrificing the smallest of their conveniences for any kind of moral reasons, and consider any suggestions of resigning from them "extreme". It's like the Louis CK sketch about the favourite thing, but with Facebook or whatever:
I no more have to subscribe to your morality as your ideology.
I'm not a bug Facebook user, but it has nothing to do with privacy. I've always known some random engineer at Facebook could read my posts, and assumed it was not a stretch for the government.
You prefer to give up conveniences because of fear of govt. I'm still much more afraid of the random engineer, but think the convenience is worth it (maybe).
Come to think of it, this is true of many causes. I recall the LGBT and atheism movements: http://www.youtube.com/watch?v=_YxdM1WChHc (She says at some point that despite the infightings, radicals and moderates actually complement each other.)
There's something off about that cosy consensus view, quite apart from the fact that it is so open to manipulation. It's basically highly conservative and only accepts the status quo.
The reality is that what may have seemed a completely out there view can become the new normal within a surprisingly short time when the environment or culture changes. Apart from politics, you see this in everything from fashion to music, business etc. (e.g. predicting the death of print or record shops, or 'did I really think I looked good in that - what the hell was I thinking?')
The world needs someone like Stallman quite simply because his views are so extreme. You need an extremist so that moderates can seem reasonable.