An award-winning cookbook author and California restaurant owner says anyone wearing a red "Make America Great Again" baseball cap will be refused service at his restaurant.

J. Kenji Lopez-Alt is a chef-partner of the Wursthall restaurant in San Mateo and says in a tweet Sunday that he views the hats as symbols of intolerance and hate.

The San Francisco Chronicle reported Thursday that Lopez-Alt's decision was met with mixed reaction by restaurant clients.

Diners interviewed by the newspapers said they understood Lopez-Alt's stance but questioned the hat ban and said he could have found a way to start a dialogue on the issue. On Twitter, many criticized the so-called tolerance of the liberal Bay Area.

Lopez-Alt wrote the 2015 book "The Food Lab: Better Home Cooking Through Science."

He says his restaurant received threatening emails following the tweet and declined further comment.