A Laguna Beach hot spot is fighting back against 7 women who say they got tossed from the restaurant because they're Muslim -- but the owner says the Muslim community is on his side.

TMZ's obtained a copy of a letter Urth Caffe owner Shallom Berkman is sharing with customers to explain why he's filed a countersuit against the women ... saying they were the victims of discrimination when they got thrown out on April 22. Video of the incident went viral.

In the letter ... Berkman says his popular establishment has always been about welcoming people of all religions, races and sexual orientations. In fact, he says his wife, Jilla, is Muslim -- and so are a large percentage of his customers.

He says they've vowed to stand by him and his wife during their legal battle.

As for why the women -- most of whom were wearing hijabs -- were "asked to leave" --

a strict 45-minute limit for outdoor seating during peak business hours, and they refused to follow the rule.