@Dave Allen,
Muslims breed Muslims, and Catholics Catholics for the same reason that English speakers breed English speakers, and Russian speakers breed Russian speakers. It is not brainwashing when we teach our children a language before they are "capable of independent thought" (although I'm not quite sure what that means; at what age are children able to think independently? at what ages are they unable to think independently?).
Introducing a child to the family's faith, to the community's spiritual rites is quite different from brainwashing the child. It is one thing to explain to a child a particular religious perspective and nurture them in a particular religious environment, and quite another to systematically impose certain beliefs upon the child with such intensity that contrary thought becomes psychologically painful and nearly impossible for the child. Brainwashing occurs, but it is far from the norm. Sunday School and Confirmation Classes are not brainwashing.
Throughout mankind's history, in every society, where ever man has traveled, there have been community spiritual practices. This is universal to humans. Look at Lascaux, for example. Spirituality is natural to our species, however we may express it.
Like you, Dave, I think each person should investigate spirituality for themselves. That each person should take responsibility for his or her spiritual life, and not submit unquestioningly to another's authority on spiritual matters. But let us be careful - do we rely want to deny people spiritual guidance? You use the phrases "parental bias" and "peer pressure", which are certainly at play in the lives of many people. But is it possible for people to influence other people's spiritual lives in positive ways? Is a parent reading to her child the Sermon on the Mount necessarily an act of "parental bias", or could it be a positive bonding experience between parent and child that helps to nurture positive moral values in the child?
When I was young my family would often go to church. I was typically reluctant, and sometimes I was given no choice but to go with them. Was this brainwashing? Or was it my parents understanding that sometimes children just do not want to do what they should do, like come home and do homework before playing outside? At every church service a collection plate was passed around - donations for the church to maintain the facilities and pay bills, sometimes a special collection for a particular cause, or maybe around Christmas money would be collected specifically to raise money for a food drive. Before each service my parents would give me five dollars, and they would tell me that it was for the collection plate. Once, I did not put the money in the plate and for this I was grounded for a whole week - I was not happy. Were my parents brainwashing me? Or were they trying to instill in me the value of charity over the instinct toward greed?
But let's also think about the influence of others on a larger scale. Let's use art as an example. While it is wonderful to find untrained geniuses, people who without formal training manage to produce brilliant and timeless works of art. But these people are rare. Typically, our great artists spend years training with teachers, studying the works of other masters. Is it possible that religion works in much the same way? That religious people can in fact benefit from the guidance and teachings of others? That spiritual education can very often benefit the spiritual life of the student? The Buddha had many teachers. Jesus learned the Hebrew scriptures well. Being a student of religion is typical among the esteemed religious figures of human history.