No, that would be fine, why not? The problem as reported in the OP was that vegans were going there and then complaining nonstop.You're joking, right? How does saying "it's not a leftist thing" and it's not a fad have anything whatsoever to do with your reply?
And please point out where I said restaurants should be all about me. Did you assume that I agree with the vegans in the article? Well, you know what they say about people who assume.
I don't demand business owners to do anything, what I do is vote with my pocketbook. If a restaurant has vegan options, I'll go there, if they don't, that's fine, I most likely will go somewhere and be supportive of those that do. Is that such a bad thing?