I wasn't quoting the Geneva Conventions. Those are actually more strict on what's a valid target. IIRC, you're not supposed to shoot at medics even if they're carrying rifles, so long as the medic is clearly identified by wearing a red cross/crescent symbol. I could Google the actual Conventions, but I'm not really all the interested in doing so. I don't run Star Wars by Earth rules of morality. The Empire shoots anyone, medic or not. Mandalorians abide by whatever their own personal code of 'honor' is (and most don't have much honor). The Old Republic and the Jedi apply situational ethics. YMMV.

A medic droid isn't a non-combatant--it's a piece of military gear and anti-materiel weapons are a thing.