And, by the way, nobody thinks his or her pet cause is a pet cause. Every pet cause is considered holy writ by the holder of the pet cause.
So yes, by that definition, pro-abortion, pro-life, and gay-rights are all pet causes. They are all single issues held by people with strong emotional feelings towards that single issue, to the exclusion of everything else, including the logic and framework of the Constitution of the United States.
that sounds like moral relativism to me