Some men, when surrounded by other men, like to behave like idiots. These men are usually idiots deep down, but that idiocy bubbles to the surface around fellow idiots. When a man can’t engage in intellectual discourse or craft witty and engaging rejoinders for his friends, he’ll resort to bantor that is more base. That bantor can, and often does, include cat-calling women.
Generally, a guy doesn’t cat-call a women when’s he’s just standing around by himself. He prefers to do it surrounded by his simple, simple friends because they’ll laugh and perhaps cat-call too. That said, sometimes a lone moron will stand on a street corner all by himself and whistle something lewd at a woman. When that’s the case, it’s all about power. That man is objectifying a woman because it makes him feel big and the woman feel small. Even if he’s too thick to grasp the psychology behind it, that’s why he’s doing it.
In short, cat-calls are much more about the man shouting them than the women they’re addressed to. Be offended, but also take pity on his malformed brain.