Some tanks have the attitude of "if you take hate you get to tank it", which is a bit ridiculous if they expect you to stop even healing. Then again, some others are just really bad.

Adjust to the party. If the tank is undergeared and struggling, but seems to be making an honest effort and does respond to advice? If he can't handle enmity from holy spam, I won't do it.

Your tank, however... vote dismiss is there for a reason.