Actually I hope they don't sue him, and I hope this sets a precedent that you really can refuse service to anyone you want, because... freedom.
That way, this guy can be a jerk all he wants and we don't have to go to his store, and a Christian baker can refuse to make cakes for a gay wedding, and that's cool too. Freedom is awesome; I'm a big fan.
I know this for sure... this jerkwad is going to lose a lot of business, but since this is Seattle after all, he'll probably get some new customers who think what he did was "fabulous". Fortunately those kinds of things tend to be a temporary spike and he'll probably close shop in a year. After all, I don't think this is atypical of his customer service philosophy...
You don't set a precedent that will be followed by leftists by caving in to them. The way to get public accommodations laws repealed is by making them as offensive to the left as they are to the right. Let the state bankrupt this homosexual hatemonger and drive him out of business.