When I tank, I really don't count my own vote. Because I play all three roles, I know exactly what queues are like for all three. Here is this poor DPS, wanting to do an exp run and having to wait 30+ minutes for a tank (maybe 15+ with a haler with him). Meanwhile this tank gets insta queues and easy living for everything except ST and WoD. So when he finally gets into a dungeon and ready for the EXP, he demands (he should have asked. WE ALL GET THAT PART) an exp run. Why? Cause 1 dungeon for him is an hour+ (queue plus the run) while for the tank, it's only the length of the run. But nope. This tank had to "teach this DPS" a lesson and say no. Even though the tank has easy queues and competence is extremely important to the speed of the run, the tank was just like nope! AND OF ALL places, in DD. The effort to grab extra mobs in DD is literally next to 0. I can only assume the extra confrontation simply budded from the first one, which wouldn't have happened if the tank didn't feel the need to "rebel" and correct some one's attitude. It's like the OP doesn't know anything about conflict resolution other than punching back. Good job bullying your party and being entitled.
And what the hell is this nonsense about SE giving your opinion more weight than any others in the event of a tie. Where was that under the description of a tanking role. Please sure me. If anything, you get less of a vote because dungeons take literally no effort for you to get in to. Yes, I've tanked and I tank often. If people want an exp run and I don't, even if it's a tie, I do the exp run. Why? because I didn't have to sit at my keyboard, twiddling my thumbs for 30+ minutes waiting for me to appear. The few mintues it takes to grab a few more mobs is literally nothing compared to how long they had to wait. And attacking a rude attitude with more rude attitude is just going to lead to them being salty the whole run and bitching at everything you say, even if it's helpful.
TL;DR: you are both in the wrong and are both entitled pricks.