Um this isn't new. They've killed lots of alledged homosexuals. They frequently seem to be throwing them off buildings. What I wonder is how do they even know they're homosexuals? Probably just like a witch hunt I bet.
This is a default position for the Islamic state, I'm more concerned about artifact destruction, and women issues
Not to say that this is not bad, just saying that with ISIS homosexual killing does not seem like such a strange thing considering what they represent, and their hatred of Western Culture that tolerates and accepts this.
As for how they know well assuming they caught them in the act, if not its a witch hunt against people they don't like or go against them.
How can you say you're more concerned about artifact destruction or womens issues? Both are important but not more than a hunman life, especially the artifacts. You cannot compare killing homosexuals to destroying bits of fancy rock (as outrageous or immoral as it may be).