I think I enjoy the pure, blatant idiotic comments sputtering outta their mouths. Most of the time I usually move or CC, if they're polite about it, otherwise...I get to be a little stubborn. Sure I know it's just as childish to have a verbal tennis match with someone over a game issue but sometimes I just need to let out a little steam.
I had an episode today in the Pyramid, two actually, with the same player. First time I moved to another map, seeing as I was helping a buddy on some quests. He wanted to go back and KS him back but I talked him out of it. Second time I was in there, I was in another party and the player from before left for a short while and came back while I was being mobbed by Skeletons

he had the usual schpiel about how he was there first and we should move or CC. I ignored him and went about my business and moved slightly out of his way. But this surely didn't suffice this person as he felt it was his duty to be a complete and utter nuisance. He stalked me and my party-mate and just KSed everything we were hunting. He went on how he would continue to KS "his" mobs until we moved or CC'ed...he was trying his best to sound all authoritative (absolute FAIL). Well, this kind of kicked my inner child into gear xD. This prompted me to shoot back with a few comments about how players don't win maps, force others to CC or move, stalk players and harass them, the definition of KSing, etc., etc.. He got steamed and started getting personal and that's where I draw the line. I can take a joke about myself, more so than some people but he went too far with some choice comments (I won't repeat them...too explicit). I told him since he's going to continue to act like a child, I'll be the bigger man, this time, and move up a level or two. He proceeded to follow me and my party-mate and continued to get more personal. Anyways, I think the best comment out of his mouth was about my age...so I kept my cool and replied how old I was and he thought it was freaking hilarious someone my age would be playing games with a bunch of kids. I was so dumbfounded by his ignorance that I had nothing to come back with.
Well, this went on for a few more minutes until my intellectual pwning eventually got to him and he vacated the premises. I know it's all silly but I think my favorite part of KSers is the verbal back and forth. It makes me laugh a little inside knowing that after a couple decades of gaming, this personality will never go away.

Sorry for the long post, I tend to get carried away at times.