I always have respect for people trying to learn how to tank. I would love to tank but just don't have the balls to try. Don't want to deal with the assholes and I don't like ruining someone's experience and waste their time if it goes horrible wrong
It's more awful trying to learn the role in older content where people just expect you to know everything because they've run the same content over and over throughout the years. People are a lot more forgiving in newer content. Granted old content up to Cata (and even then it's largely just TW) is just tank and spank and a complete faceroll with heirlooms but you don't know that starting out and likely don't have heirlooms.
But even if there are assholes, or the entirely possible fact that you throw a dungeon run under the bus because you do badly, your next queue to learn and improve is mere minutes away, while they await 45 minutes. There's never a better time to learn and give it a shot than now. My experience as a first time tank main has been overwhelmingly positive, I found that to be true of healing as well.
I think I only want to play hybrids than can do everything moving forward. Even if that means being a predominantly melee player and only playing Paladin, Monk and Druid.
If you want to tank, just do it. Odds are it's the DPS that will ruin your experience. At least that's my experience over the years.
In my brief experience Warlocks and Hunters are usually the most problematic DPS classes to play with because half the time they don't turn growl off on their pets, sometimes even when asked. Then you have to fight to maintain aggro and it starts to become real work. I just let them take the aggro if the mobs are only going after them.