The analogy works fine. We have the politically motivated FSF on the "meat is murder" side, and on the other hand the Open Source movements belief that open source is simply a more practical way to develop software on the "healthier lifestyle" side.

I wouldn't expect PETA to stop with their off-putting campaigns ("Your Mommy Kill Animals"), it is what they genuinely believe, and for them keeping silent and advocating "a healthier lifestyle" would be so far from their viewpoint that it would practically be a lie, even if it might win them more friends and influence.

Same with RMS. His views are radical, and toning his messages to make them more palatable down would be dishonest to who he is. Let someone else play the moderate and practical.

Of course, moderate and practical people don't dedicate their life to a message, be it "a healthier lifestyle" or "a better way to develop software". The Open Source spokespeople like Michael Tiemann or Tim O'Reilly) tend to get distracted by having a life to live.