Show them a Direct Defiance video on youtube :D
But seriously, good on you for leaving. Ask your Druid ex-guild leader if he's geared enough to double-tank Attuman & Midnight together, Moroes & a Warrior add together, Romeo & Juliette together, 3 of the Crone mobs together, and Illhoof + his imp + ALL of the portal imps together... You EASILY are.
Before my current set of chars -- I had a pre-BC pally that occasionally specced to tank. The stereotype was actually deserved then.. you could be good but you didn't have the inherant potential of a Warrior.
I took a bunch of raiding newbs, and with LOTS of turnover pulled one or two useful people out of every dozen over a long period of time. Together we learned the new progressions, and they learned to do things with a Pally heading up the tanking corps. You have to put up with WAY more crap from people after you get into Tier 5 than you do in Kara especially.
I get that tingly feeling when a guild member sends one of the kill videos he's made to a trash talker who can't wrap his head around Paladins tanking in end-game and the fool realizes "wow -- this is WAYY smoother than when we run it..". Instead of making fun of their tanks, I just tell them "It's not because of the class of the tank -- it's because of the group".
We learned to play together, we know eachother's strengths and weaknesses. A Pally tank has to fight SO hard for respect that they sometimes try to take on more than they can handle. ANY tank needs to know when to step back and ask another tank to take over in a particular encounter. If everyone doesn't respect eachother (which is what your old guild sounds like) a group will NEVER reach that kind of compatability. I am honored to tank for the people that I play with because of the respect. They stand up for me and other pally tanks the way I keep giant fat monsters from utterly destroying them.
Don't let yourself fall into a group that doesn't respect you or what you can bring to the situation. Start from scratch and put together a group of people who are TOTALLY new to end-game if need be. Work with them and shape the group together. Learn together. Learn what they bring to the group, and always respect them.
I hate to see when Paladins get the shaft in this regards, but I ABSOLUTLY hate to see when it's the Paladin that's disrespecting people and going ape@#$% on them. Usually it's a Pally without a spell damage weapon who completely sucks at doing his/her job too.
And yea.. bodhisattva knows all about bad guilds :D But he's a Buddhist going by the name, so he can handle the stress... right?