I've always thought the people that hate Xur and think him selling Gjallahorn would be the apocalypse were a little silly. I think I finally figured out why they are like that. They are just insecure. Before the Gjallahorn they 'earned' through RNG made them special and was a reason why people would pick them over someone else who doesn't have one. Now that potentially everyone has a G-horn, on some level they are worried they aren't skilled enough to be picked based on their ability.