From the discussions I've had, they see it as their land that the Kurds are trying to take from them. Of course, Turkish pan-nationalism even claims the Baltics and western China as their native land so take that with a grain of salt. Claims that Kurds are uneducated, religious fundamentalists with large families they can't provide for and will ruin* and overrun the country with their customs, etc.

As others said, racism and fascism. Typical Turkish nationalism.