If a corsair finds goodies they want on a hessian they'll just blow up then hessian to get at them. Especially as both factions hate each other...
As for the warning, a simple 'Die!' or 'Die insertfaction/playername!' works fine.
As far as attacking goes... I'd use the server rule about self-defence, specifically the bit about having to 'drain your targets shield to under half-power or do hull damage' for it to be classed as attacking.
These aren't rules or anything, just pointers of things most of the pirates who don't get flamed on the forums use, quotes from rules etc.
If you don't want to follow them, fine.
As for the xeno's only having to pirate zoners and IMG, I agree, however after getting flamed for blasting everything in sight as a [Phantom], regardless of ID, I figured I'd let people know what I found that works.
I agree with the point though, why players who have freelancer and neutral ID's think that will keep them safe from anyone and everyone is beyond me.
Unless a freelancer or neutral player has some sort of agreement with the xeno ID'd player then they should be fair game.
Also the Xeno ID is the only one that states that you can engage anyone and everyone without warning them first.
The other pirate/terrorist ID's only say that you can pirate with them, not that you can go around blasting everyone in range.