It's more rivalry than hate. I haven't gotten any this time around but in the Alpha had a lot of gear with similar comments. It is more just the way they think and act. Warlocks are more calm collected and seek knowledge. While Hunters are out in the wild getting dirty not always following the rules and have those super flashy capes. Hunters are essentially the wild children and the Warlocks are the mature studious ones. I haven't heard it this time but in the Alpha the Hunter Vanguard also made some funny but not-mean spirited remarks about Warlocks.