Yes, it is discriminatory.

Just as a restaurant that only serve fish discriminates against non-fish eaters. Or vegan restaurants discriminate against people who want to eat meat. That does not make it illegal.

Amusement parks discriminate when they establish a minimum height for rides.

Bars discriminate when they say you must be 21 to enter.

Stores discriminate when they post "no shoes, no shirts, no service."

Discrimination is not illegal. Certain discrimination is.

I have read the restaurant is getting overwhelming support.