If the choir director is pushing you to do something you feel is unhealthy for your voice, decline to do so--or just leave.   There are likely to be groups more to your needs.

And the more desirable you are as a singer, the more likely you can get into the group you want.   That's why a bit of music theory is useful, as well as extending your range--to make you more saleable.

But if anybody has any real stories of how choir directors have endangered a voice, I'd like to hear them. Most of the stories I've heard are from the opposite perspective--of the problems of choir directors.