this idea is at the core of books like 1984, for example.
Calling rap music "c...rap", calling them useds instead of users, the gravmass stuff, writing diatribes about not wearing ties, not to mention eating his toe jam on camera that one time... He's a kook and will never be taken seriously.
Like it or not we are superficial beings and culture carries with it certain norms that must be adhered to if we wish to maintain broad spectrum appeal or credibility.
It's not enough to have good ideas.
His organization offered another way. He never thought it would get off the ground, but it turned out that corporations are desperate to save a buck and are more than willing to work with free software in order to do it. The GPL was the first keystone, his advocacy helped to popularize it.
His choice of appealing to nerds like him was perfect, and his kook persona where he doesn't bother trying to button up his rougher edges is far more convincing than any amount of sanitizing ever would be.
More to the point, Stallman is insanely smart, and is more accomplished than probably anybody posting on HN, including even pg. He didn't stop being smart just because he became notable.
"c...rap" is the most obvious example of this cited upthread. de gustibus non est disputandum, man; spend more time talking about more objective things with objective tone.