So you wanna know why icon creators get worked up over their icons getting stolen??
The reason people get so pissed off when their icons get stolen is because good icons take lots of time and WORK to make. It's a lot more complicated than cropping a picture. To advertise an icon you like without a word to the creator or even "I don't know who made this, but if you do let me know" you're giving the false impression that you're the creator of the icon, and it's just flat out rude!! Don't tell people to chill out just because you're too flippin lazy to make you're own icons or even drop a note of appreciation to the creator. Why don't you go look up icon tutorials
and try making your own icons before flying off the handle and telling icon creators to chill out. It might make you appreciate great icons a little more.