There are several reasons for the tension in the in-game lore. Let me tell you a tale. Long ago, the first guardians where the Warlocks, who studied the traveler and unlocked its secrets, and the power of light. Then came the titans, who where blessed with the light in order to defend the traveler and it's flock. But then there were the hunters; the rogues, the scavengers, the nomads, and the thieves. Now, understandably, the Warlocks were a little ticked off at this; why should these people on the fringe of society receive the same blessing as those who devoted their lives to understanding and unlocking the ways of the traveler? It was insulting, demeaning to all of their work and dedication, and a slap in the face. Warlocks feel like the mere existence of the hunters is a slight against them, and due to their very nature, Hunters don't really fit in very well with society, and bashing on warlocks gives them something of a common ground. From those early days, the rivalry between the two has only gotten stronger. Hunters have even [url=http://destiny.wikia.com/wiki/Aphorisms_to_Anger_Warlocks]written an entire guide to angering warlocks[/url]. Now, if we're talking about why there's a rivalry between them in the community, it's because class differences are one of the easier things to fight about. Everyone has one that they prefer, and when one person prefers something, they'll defend their choice and put down others choices to the bitter end because they don't want to admit that maybe, just [i]maybe[/i], every class has something to offer.