Why is there so much MS hate in the world??
A couple of reasons (as I understand it):
1) They're Microsoft, and they don't care!
2) You can't buy a computer without Windows installed.
3) They upgrade and change file formats on a whim, and if the rest of your group doesn't upgrade, they are hopelessly lost with incomplete compatibility.
4) Many of the commenters like Linux.
5) It is an easy target.
I suspect that reason #5 is the most common. Others will probably add reasons in future comments, feel free.