It needs to go if the vehicle becomes a combatant vehicle. The crew using personal weapons in self defence doesn't count, but medevac helicopter equipped with weapons to lay down support in hot landing zone is no longer a vehicle that can claim protection of red cross/red crescent, but a valid target for fire.

It's literal. The red cross is supposed to mean that it's humanitarian, neutral and carries no weapons.

You don't see them medevac-ing the enemies, so they are not neutral.

A big reason for medevac is to free soilders from caring for the wounded, so they can continue firing weapons at you.

Neutral seems like a crazy idea to me. It's a critical part of the offense.

Do you see a lot of medevacs?

The Geneva convention basically states that whomever the injured is in the care of is charged with giving them adequate care. If that care requires medevac it's going to happen.

The protections accorded the wounded and sick apply to friend and foe alike without distinction

https://armypubs.army.mil/epubs/DR_pubs/DR_a/ARN31133-FM_4-0...

https://ihl-databases.icrc.org/customary-ihl/eng/docs/v2_rul...

Have the opponents of the last few decades of us war followed Geneva conventions?

I don't see it, so it does not exist?