I know several Catholics who have no problem using a transgender person's pronouns. Trying to use a religion as a cover for bigotry is disrespectful to both the transgender person and other members of the religion.
Oh the Bible isn't the end-all-be-all and you need someone to make an executive decision sometimes? Who's that?
The Pope? Oh you're not of that kind of denomination? What about the President of the Mormon Church?
That leaves it up to personal interpretation and opinion. Considering that the overall message of Christianity is supposedly something about "love and grace" the not transphobic opinions are a lot more compelling.