There are A LOT of people that hate Apple out of ignorance.
Being friends with a lot of gamers that build their own PCs (I build my own Windows PCs for purely gaming too), they tend to hate Apple since they aren't the greatest with gaming. If I asked any of them why Macs weren't great for gaming, they wouldn't be able to explain it to me. All they would say is that that's all they've heard. Most couldn't tell me about Bootcamp or anything of that sort.
Others can't justify the price and state that they are overpriced and that you're only paying for an Apple logo smacked onto a pretty computer. They won't accept that the Software (OS X) works so much better with the Apple tested hardware than Windows which has to work on several different combinations of hardware.
Like others have said, since OS X is always advertised as being easier to use, many will state that it is for those that are stupid. Their only argument against OS X not getting viruses is "well, it would be pointless to make viruses for Macs because Macs are stupid!" Great logic, right? They haven't experienced what it's like to (nearly) be risk-free from viruses. They haven't experience the intuitive gestures and they just assume it's for "dumb" people.
Many also have not even tried out OS X. They have just been using Windows all of their lives so out of ignorance they just assume that what they have is better. I have a friend who is that way. I'd like to see him import thousands of photos onto his computer and have it nicely sorted out.
I even have a friend who calls Apple a bunch of "communists." That is the most ignorant reason of them all. He just can't accept the fact that OS X is closed source and that the Apple Ecosystem works super well.
Many think that Windows is better because there is a larger quantity of Windows Programs available compared to OS X. They don't realize that Quality is more important than quantity. For example, their iMovie equivalent is Windows Movie Maker
.
I took a couple of friends into an Apple store once because one wanted an Apple TV for his room. My other friend said that he felt "out of place" in there and that everything in there was a waste of money.
I should really invest in some new friends, huh?
Mainly, I think Windows users feel superior because they have never tried OS X and associate it being for "dumb" people that need a simplified OS.