Then do not let a root of bitterness rise up in you. Forgive the offense of this younger brother and do not be a stumbling block for him. In fact, the best offer you can make is to be his prayer partner - meet with him weekly over coffee and offer to be his Paul/mentor. This will allow you to (over time) help him discern between truth and error, good and evil as you search the scriptures together.
If none of this works or you meet arrogance/resistence...send a letter to the elders indicating your resignation and why. Then go in peace.