There’s a variety of Christian concepts of what it takes to achieve salvation, and someplace an emphasis on works (such as water baptism for infants or anyone else) while others don’t.
Salvation is a gift
The reason for that is no mystery if you realize that while some Bible verses seem to be straightforward that salvation is a gift free for the taking, others warn about the kinds of things that keep someone from being saved or are a sign of the end approaching, and still others show a clear difference between what it takes to gain initial salvation and what salvation entails.
If nothing else, understanding all of this helps to put things in a reasonable perspective for genuine Christ-followers: neither trying to be saved by their own works nor banking on once-saved-always-saved doctrine (even if it turns out to be true), the latter of which can lead to entertaining the idea that they can keep doing whatever they want and expect to be in good standing with God in the end simply because they’ve prayed a form of the sinner’s prayer at least once in their lifetimes. Jesus even said that the path to God is narrow and not a shortcut.
The Savior of All
One especially major point of controversy has been what Paul wrote about salvation in 1 Timothy 2:15. You’ll get the wrong ideas about it if you don’t take care to put the verse in its proper context, which is important not just here but everywhere else in the Bible, too. Al Maxey’s conclusion on it is that “the problem is solved if Paul had in view the birth of a child, [W]ho would be the Savior of all. Our response, therefore, whether male or female, is to live a sanctified, self-restrained life, one evidenced by faith and love! This has always been God’s desire for His people, and through the birth of the Messiah, He has achieved our redemption. It is here that we must place our trust.”
People within the body of Christ
People within the body of Christ also don’t seem to agree on whether or not there’s such a thing as the Rapture (the “catching away” that according to teaching will take saints and children straight to heaven and leave everyone else behind; however, George Zeller’s critique of the first Left Behind movie opines that such an event, which he still believes to be real, won’t actually be as catastrophic as the movie portrays it). Many of them insist that their position on it is the right one, and allow that position to guide their conduct in the here and now.
Historically, there have even been groups such as the Manichaeans (of which St. Augustine was one before converting to Christianity) and the Cathars who placed a lot of importance on this conduct by teaching that given both history and what lies in the future, no matter how you look at it, procreation is one thing that perpetuates the cycles of evil and the rebirth of the soul which are unacceptable since the world itself is hopelessly corrupt and beyond redemption.
As Gnostic groups, some of their teachings and practices were no doubt strange or offensive to outsiders much like the ones of today’s Church of Euthanasia (which is actually a political rather than religious group). Even New Testament warnings against Gnostics were written that stopped short of mentioning them by name (see, for example, 1 John 1:8-10). But from the perspective of anyone who believes in a divine plan of salvation, abstaining from procreation to bring about human extinction is still something that will speed up the final completion of that plan.