I have never grasped picking as a separate category of misdeed.
If one swoops in and clears a friendly's 12, then that is rather rude because it is a 12 clear, not because it is a "pick".
If one swoops in and clears a friendly's 6, that is generally regarded as what one is supposed to do. The enemy pilot may be miffed, but that is the game.
If one swoops in and kills a guy with 3 friendlies already on him, then isn't the applicable term for the misdeed "ganging" rather picking?
And if one races through a larger number of reds and blasts one or two out of the sky because their SA was non-existent, why then this is the noble deed of thinning the horde.