Dorne wants Aerys on the Throne, but is a Kingdom of the Red God. So ask yourself, King, or God? This is a Medieval dilemma; a very, very real one. What do you give priority to? A Kingdom that is in the wrong, but is with your religion, or a King that you support, that isn't? We cannot tell. One option is total war, the other is the Crakehalls seeing themselves get kicked in the stomach. I doubt that Garland would want Tyget dead, though, and he has a remarkable amount of power. Fool's move, or not, is your choice. 

Also, RIP Daenys Targaryen. Wow....we killed him. He's fucking dead. Holy shit.