They are probably the strongest pro-life group there is. That last statement is only a half-truth. The Roman Catholic church has been losing members by the tens of millions in the last few decades. Forcing the Catholic woman not to use birth control devices and prohibiting abortions has been the greatest evangelism tool the Roman church has had until recently. It has grown from within.
Catholic families tend to be larger than Protestant families.
To become the ruling institution of the world, it must have people, billions of people. The works-centered teachings of the Roman Catholic church bring children into the world and never allows them to come to life. It has a gospel guaranteed to keep everyone dead while thinking they are alive. Jesus said he came that we may have life. There is very little life in the Roman Catholic church.