Oh, they figured their way out of that painted corner a long time ago. All they need is Matthew 5:17 and the Old Testament in order to justify any atrocity.
Whenever they are tired of the whole love thy neighbor/turn the other cheek/cast no judgements side of Jesus, they just bring up Matthew: he didn't come to DESTROY the OT law he came to FULFILL it!
That's all it takes to make it OK for them to smite enemies and hate people for their sexuality.