As I always like to point out, if you actually care about “why Muslims hate us” and if you actually read jihadist forums, you’ll see that they mention gay marriage at least as often as Palestine or the Iraq war.
People should never forget that SSM is deeply offensive to probably 90% of the world’s population, and a wholesale embrace of it will have consequences.
The problem though is that homosexual acts are largely tolerated in much of the Muslim world. Perhaps this is one of the Sunni/Shia differences.