"Marriage is already facing a number of challenges, and anyone with an ounce of common sense can see that families and society are weaker and poorer as a result.
"What politicians should be doing is looking at what needs to be done to strengthen marriage, not spending time debating bills whose main outcome would be to further undermine it."
Mr Carpenter urged anyone concerned by gay marriage to write a submission opposing it "and to do so with language and a tone of voice that is gracious and respectful".
"It is possible to talk so much or speak so loudly that people can't hear what we are saying," he said.
"It is also possible for language to reflect a tone of voice which does not communicate the love we are called to display."
The Marriage (Definition of Marriage) Amendment Bill to allow same-sex couples to wed has already passed its first reading in Parliament.