Why is Islam hated?
To the degree that Islam is hated, it is hated, I would say, by people who fear it because they know nothing about it. We are fearful of the unknown and tend to hate that which we don't understand.
There are people who will say that Islam is hated because of its history, the Islam conquest of part of Europe, for example, but there is really no religion immune from some history of conquest--for example, the Crusades, so that does not satisfy me as an explanation.
There are people who will say that Islam is hated because of ISIS and the other radical movements by a few people who claim to be acting on behalf of Islam. But these movements are about power, not religion. Israel, under continuing existential threat from people who happen to be of the Islamic faith, does not hate the Islamic faith.
What has happened is that Islam has come to the attention of the western world again because of various radical terrorist groups, and now that it has come to our attention, we have chosen to demonize an entire religion about which we know little, and that which we do know focuses on superficial differences. The fact is that in the Western world, as far as I can tell, there is little if any effort to help people understand anything about the Islam faith, so our ignorance, fear, and hatred persist. This seems to me to be a vicious cycle. The more we hate, the easier it is to radicalize people, and then people feel justified in hating even more. The cycle can only be interrupted with knowledge and understanding.