The ELCA health plan covers employees of the Evangelical Lutheran Church in America which includes "rostered leaders, lay church workers, retirees, and family members..." (see below)
The money which members give to their local ELCA church, intended for God's use, will now be used to pay for the sex-change operations of ELCA employees and their family members who want to change their gender. (a desire that is medically impossible)
Instead of helping struggling people embrace the way God made them, the ELCA wants you to pay the bill so a man can try to look like a woman, and a woman try to look like a man. Mutilating and abusing their body on your/God's dime.
Don't forget that the ELCA health insurance also covers abortions for ELCA employees and family members, a fact that has upset thousands upon thousands of members. Forcing Bible-believing ELCA members to pay for sex change surgery, etc. should do the same.
(Update: Below you will see a Portico Benefit Services document for 2017 stating more details of their transgender related coverage.)
Here is a closeup of the highlighted section about gender reassignment surgery that is covered:
Also, you can view the Executive Director of Extraordinary Lutheran Ministries comments about ELCA/Portico's decision here.