I'm afraid Irish people who have spent time in Australia tell me a different story. They tell me of having comments similar to this man's being thrown at them in job interviews and by employers,
I'll take your word for it. I don't doubt that it happens at times, but I've never encountered it. This leads me to think it's not many people who would behave like that.
and of media editorials in the aftermath of the Boston bomb insinuating that Boston deserved it because its a city full of Irish-Americans, and therefore a city full of terrorists.
I'd like to see examples of that. It sounds like the sort of thing you might find by trawling the arse end of shock jock blogs.
And yes, I think this man despises Irish people, and I think you're being far too quick to dismiss his words as all a big joke.
The problem I'm having is that your claims just don't match the evidence, as far as I can tell. You've said he wants to make the Irish seem "despicable". Ok, say you're on a mission to make some group of people seem despicable. How would you go about that? Presumably you'd start by accusing them of truly despicable things.
Let's say I wanted to make Hassan seem despicable. I'm sure he must be, because nobody could be that nice so he must be hiding something, but I need ammunition. So I says to you "Cheetah, me old china, I know how to make Hass seem despicable!" "Fukn bonza!" you say "Tell me more!" "K. I'm going to start by accusing him of a/ using a four-leafed clover as a personal symbol and b/ talking funny and c/ not being a particularly effective gardener!"
"By fuck" says you "that'll totally work. Those three characteristics are so totally despicable that everyone is bound to think Hass is lower than a snake's arse!"
Except that you wouldn't. You'd be saying something like "Fucking what?"

You see my problem here? Your claim doesn't match the evidence. If you want to slag off this bloke off for stuff he's actually done that's fair enough, but you seem to be wanting to slag him off for stuff that, as far as I can tell, he hasn't actually done.
On reflection I'll grant you that he may have been a bit out of line with the spuds thing, but I still think you're taking the rest of it far too seriously. If he wanted to make the Irish seem "despicable" I very much doubt he'd be using "insults" that could have come straight out of Monty Python and the Holy Grail.
FWIW, this incident has been getting bugger all traction over here. Most people seem to not give a shit, or not even know, that he has said anything at all about any subject. The only outrage seems to be coming from a few Irish sources. Most of the first page of search hits on his name, when you ignore the non-Australian ones, are about a couple of years back when he called Leigh Sales a cow. He's just not a major player in Australia public opinion.