People should definitely try not to be jerks about it, but they did teach you something you didn't know. Why would you not take this new information and try again? Quitting ranked altogether because someone was mean is, well, silly. Why limit your access to the game because of a couple random people?
Did you at least go back to unranked and put this information to use instead?
This highlights a more pressing issue.
People may jump into ranked without knowing their role/class well enough. A Tank's role is pure utility in PvP, damage sponge, guard swap, and seperation/disruption. Normally you'll learn to guard swap in warzones very fast because there are 8 people and you have to constantly swap guard.
So, while he shouldn't be completely flamed for it, there is an expectation when you enter a ranked match that you've done your homework already. It is very unfortunate to just give up, though, because people are just as vicious in regular matches as in ranked matches. No avoiding those kinds of people, just rolling with the punches.