You should know that the thing that pisses off workers most is unfairness, not inequality.

what pisses workers off has nothing whatsoever to do with the economy. Also, unfairness and inequality are the same thing.

So I don't like seeing someone less qualified than me making more than me. Is this wrong?

It's not a question of what is wrong or right. I think your perspective here is 1) naive and 2) unproductive. It's naive because you think the universe should work how you want it to work. It doesn't. It's unproductive because, instead of solving your problems, you're choosing to bitch on reddit about a circumstance that you have no control over.

Wouldn't your resent management in a similar case?

Nope. And I get systematically undervalued and underpaid because I'm a woman (and this would be way worse if I were in Italy). If it was a manager who revealed your colleague's salary, that was in extremely poor taste, of course.