Definitely not all Irish would be offended, up the north in the tense areas yeah probably.
But having said that I dont know anyone who'd wear clothes with a union jack on it, so maybe theres a little dis taste for it, but I wouldn't call it offensive
On the other hand, the only people you see wearing the Union Jack in the UK are tourists, weirdos obsessed with the royal family, and members our borderline fascist political parties.
