Hunter is the only class that focuses on long range and headshot precision damage skill, which are the traditional run and gun associated tactic skills, think about the idea that BR effectiveness would determine just how "skilled" you were at halo. The hunter has a similar stigma associated with it. It literally has a perk tree focused on making your gun more accurate and upping reload speed when you get precision damage. The other classes certainly take skill, it's just not precision focused. Warlock is really AOE damage to control enemy movement and Titan is short range chase people down quick reaction time skill. You have to understand that a lot of 11 year olds associate skill only with guns, in fps games, they have absolutely no understanding of strategic roles or effective ranges. The other portion of this stigma comes from the idea that if you can't hit precision kills, the hunter won't reward you the same way a Titan or warlock would for just getting raw kills. The long range is hard to mess up at, but it's also very easy to waste time. To be honest I don't think the idea is that hunters are skilled, I assume that the good ones, the same with warlocks and titans; will need to be good at their class strengths, a skilled hunter is going to need to understand the roles of their team while being deadly at range and smart about taking on the other two classes that can obliterate them at mid-short range.