Dandi,
You make some extremely good points here and I can find nowhere where I could disagree with you. Your comment about Catholic baptism makes one think that there must be a purpose to their infant baptism other than what they claim.
If there is a religion that cannot ever be catholic, i.e. universal, it is the faith of Christ. Because Jesus said that everyone is called to follow him, but few would actually do so. So, whoever claims Christianity to be a
volkskirche, thereby identifying populace with church, cannot be speaking the truth, cannot even know who Jesus was.
And the likelihood that a whole continent of people will willingly give assent to the same religious belief, whatever it may be, is too improbable to be taken seriously. Europe became Catholic because to be otherwise in Europe was to be persecuted, to banishment or death. Europe became 'Christian' so that it would never become Christian, even in part. The good is the enemy of the best, and the good, in this case, was all on the surface, mere whitewash hiding a sepulchre of corrupt rulers and rules.
That is the background to Catholic water baptism. Infant baptism was one of the means by which Christianity was suppressed, not propagated. In apostolic times, water baptism was the means of making public show of one's faith. So when Peter told the people of Jerusalem, "Repent and be baptised, every one of you, in the name of Jesus Christ for the forgiveness of your sins," he meant that
if their sins were to be forgiven, they must not only believe, but they must show that they believed, and were willing to be persecuted for following Christ. Paul echoed him in Romans 10:9:
'If you confess with your mouth, "Jesus is Lord," and believe in your heart that God raised him from the dead, you will be saved.'
Both of them confirmed the words of Jesus:
"I tell you, whoever acknowledges me before men, the Son of Man will also acknowledge him before the angels of God. But he who disowns me before men will be disowned before the angels of God." Lk 12:8-9 NIV
The worldly are very far from this, as can be imagined, and as indeed they must be. Later, Peter wrote that false teachers 'will secretly introduce destructive heresies' (2Pe 2:1 NIV), and that 'many' would follow them. One of these tall tales was that water baptism, rather than being a consequence of conversion, effects conversion; that one becomes a Christian by being wetted. A preposterous notion, but the fear of Christ drives evil men to apparent insanity. And if getting wet would get an adult or child to be in Christ, why not infants, who could not argue about it? And so, the world became Christian, because merely to be born was to be Christian. So there was no sanctification, no real opposition to the progress of evil people in their wrongdoing, no 'salt of the earth'. While there was no sanctification as experienced by those in Christ, there was, for the typical baptised, social pressure via priest, family and villagers that produced a limited sort of morality. This was called the value of 'Christendom', and was undeniably useful for helping to keep a sort of social order in undemocratic states. But Paul wrote about the rules of this sort of religion having
'An appearance of wisdom, with their self-imposed worship, their false humility and their harsh treatment of the body, but they lack any value in restraining sensual indulgence.' Col 2:23 NIV
The Reformation of course brought about the realisation that all this religion was just as Peter and Paul had prophesied, and that infant baptism was nugatory and invalid. In time, the number of 'cradle Catholics' fell, and the Vatican was competing for new members, along with others. There was criticism from Protestants that the recruitment of adult members was too easy, making Catholicism a 'cheap' belief. So this process was made more difficult, and prospective Catholics were to be catechised with much greater thoroughness. So Catholicism now looks more credible, in one sense; but the contrast between the requirements for 'trained' adult converts and the infant baptised looks even greater. Today, because social pressures are far lower, cradle Catholics are often wildly un-Catholic, as far as beliefs go. You can be a Catholic and claim to be Buddhist, or even atheist, also; and nobody will stop you. That alone tells the observer how valuable water baptism is, outside the authentic apostolic practice.