Sticks and Stones....?

Here in Northern Ireland we have a particular strong vocabulary for using derogatory terms to describe the 'other' religion.
You have the usual Fenian, Taig, Orange Bastard etc. All equally repulsive and most factually untrue. e.g. The Fenian movement disbanded many years ago, i believe and contrary to popular belief a good percentage of Protestants are not members of the Orange Institution. Most probably know their fathers as well i would presume?
I live in a very sectarian corner of this green and unpleasant land and lately I've been puzzled by some of the graffiti which appears on a regular basis on my gable wall.
Firstly there was A.H.A.T. It didn't offend me because i didn't have a clue what it meant.
A friend of mine has since informed that it means 'All Huns Are Targets'?
Apparently Hun is now a derogatory term used to mean Protestants? Yes, I'm confused too.
Back in the day, when i were a lad, Hun was a term used in comics and films starring Clark Gable, to means Germans during the 2ND World War? What connection this has to Protestants remains unknown.
Another even more confusing one was 'Black Bastards'. This, i again wrongly assumed was some sort of racial remark against our coloured cousins? Apparently not. I'm reliably informed that 'Black' is another term meaning Protestant?
I'm really confused now.
I've no objection to be verbally abused (well i have but you know what i mean), but can it be considered offensive when the recipient doesn't understand it?
As usual, answers on a postcard...