Jekyll in RL it's a waste of time, ammo, and effort to kill someone in a chute. The threat a chute poses to a mission is so miniscule that someone in a parachute wouldn't be considered a valid target, especially given the kind of air superiority the USAF currently enjoys.
If we were in a life and death struggle with another nation and I knew that the other guy was going to return and attack me, my comrades, or my country, I'd follow whatever ROE my commanders set up to and including blowing the bastage out from under his chute if that's what it took to get him out of the war for good AND the rules of engagement authorized it.
Frankly I think we'd have to be losing pretty badly for the ROE to authorize shooting people in their chutes, but I suppose it could happen.
In the game though, there's no moral question involved IMHO. If it can be killed, then it's a target in the game.

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eagl <squealing Pigs> BYA
Oink Oink To War!!!