I think you guys do this guy too much credit. He's not a neo-Nazi, in fact he probably doesn't know what Nazi means, other than it's foreign, and therefore, bad.
What he does know is that whatever he has done wrong, there are soldiers involved, so when he sees them, he does something that he hopes will offend them - in this case the salute and saying 'Up the IRA'. He probably isn't a big advocate of Irish independence either, but he knows that Hitler and the IRA killed British soldiers, so he uses them to taunt soldiers. It's no different to the way he probably taunts the police when he's out on the town. He's a moron, and an ill-educated one at that, and his sole aim in life is to offend and provoke. Any media attention he gets is too much. He just needs to be left to rot somewhere out of the way of functional society...