It's not vegeterianism that is objectionable, it's the attitude of certain vegetarians. It's not feminism that's objectionable, it's the attitude of certain....well, you get the idea.

...This would be a good response, except that Mr. Orwell's comment refers to "every fruit-juice drinker, nudist, sandal-wearer, etc etc pacifist and feminist in England." You're discriminating between good and bad ones in those groups; he explicitly isn't!