Arrogant maybe if it said "the best." But it didn't, it said "ours."

Offending maybe if it said "Shit legal systems." But it didn't, it said "Legal systems."

It isn't really reaching to make a few assumptions. On an English speaking website, owned by an American accelerator in California, with a majority of American users, is it hard to assume that "ours" means "American?"

English, unfortunately, does not distinguish between these cases. “Ours” can mean “mine and yours” or it can mean “mine and that of some other people.”

The author clearly means the latter, and you’re getting offended over your own misunderstand.