Exactly, I make it a point to check the ID of any ship I pass in all my characters.
If it's got an ID from a faction that is hostile to the faction ID I'm using then I attack it, usually with a warning.
Though any players flying pass my characters with a faction tag that is hostile, or if they are red on my HUD, will be attacked without any warnings because they are hostile.
I still try to check their ID first, unless they're already shooting me.
If I find a faction ID that has no relation to the tag they've got then I ask them about it, if they didn't want their current tag or are trying to change it I leave them alone.
As for the question, it depends on the circumstances.
If the factions are suppose to be friendly and a player from one attacks a tagged player-trader from the other then I'd say that it's grounds for a revenge strike at the very least.
If the player-trader has nothing to do with any other faction then it's just piracy or terrorism.
But people still have to check ID's and remember that you can only attack a neutral, freelance or zoner ID'd trader if they refuse to drop cargo.
Plus you shouldn't really be pirating traders ID'd as a faction that is hostile to the ID your using, you should be shooting them on sight because they are hostile.
It mostly boils down to using some common sense and thinking before reacting.
You can always PM the leader of whatever faction the player doing the shooting/pirating is in to ask whats going on, if it was a member acting without orders, or a mistake then it'll be solved without a faction war.
