So you let them treat your sovereignty like a joke and have them execute them on your soil without you knowing?
You don't even need to hand them over, you can expel them, tell them to go to a different country like Tajikistan or elsewhere.
And even if you sent them to Afghanistan, so what? "International Image" who would think less of Iran? A bunch of these countries send Uygurs back to China, and they kill their own dissidents, the ones who would complain already hate Iran to begin with, and the ones that don't wouldn't care either way.