This is exactly what lawsuits are made for. That's clearly islamophobia in its most blatant form. It also happens to show the great utility of the word "inshallah" ("God willing") in the Musilim parlance, especially these days. If you don't make it, you can at least say, "well, God didn't will it this time". Unfortunately, it seems that they'll be getting a lot of mileage out of this excuse, especially if Trump gets his way in the elections...
I hope Southwest is gonna lose a few millions of dollars over this. Fortunately, this is the kind of lawsuit that is generally known to work in the US.