fanaticism....yes....we even see that here on FR from time to time.
There is a strong totalitarian streak in too many people pushing whatever cause they believe in.
It sounds like this writer is a vegetarian, for whatever personal reasons, but does not want to impose that status on others.
Face it, whether the issue is homosexuality, saving the whales, global warming, alleged racism, or any other cause you can think of, the loudest most active people are also the most obnoxious and most totalitarian in their thinking. And if they had the power, those supporting those causes want to impose their views on the rest of us.