The answer is in a couple things.
For one, many Windows users don't hate Macs -- mainly the geeks do, however. And also, there is a certain generation of people who don't like Macs. There was a time where Apple wasn't making very good products (during the mid-90s), and these products were in many schools where kids were growing up using Macs.
These Macs had many problems, would freeze all the time, incompatibility... etc. The students of that time have now grown into their 20s, and many of them are still scarred from what they grew up knowing about Macs.
Things have changed a lot since then, and the current generation of kids in schools are seeing Macs for being the great computers they are. When they're in their 20s, the computer world will be a very different place.