This is not accurate, and I want to shed some light on human brain development and how brainwashing and cult mechanics work. The reason I'm saying all that I've said below, it's not an attack on anyone, it's just that I studied Anthropology in college, and Psychology as well, plus have taught children for 15 years so these are things I have to be knowledgeable in, in order to do my job. Not that understanding the sickness behind cult mechanics is necessary to teach a 2 year old, cause it's not, it's just one of the things you come to understand after delving into these subjects for many years.
Age 7 - 8 is a point of maturity for young people, when they cross over from early childhood to adolescence, and begin grasping empathy and common sense. Personality continues to grow throughout childhood, teen years and adulthood. This is based heavily on genetics, education, and economic status.
Plenty of adults have been brainwashed and programmed in adulthood. Humans are naturally social and crave a sense of togetherness and belonging. This is why the pandemic has caused a severe laziness in society, because humans become "depressed" when they don't have typical social bonding for long periods of time. A classic example of programming is the Jim Jones massacre. JJ used specific techniques to preach to people, inspire them, offer them warmth and promises. Then he took their money. Praised them for giving to him, for contributing to their cause, which caused those people to feel like they made a difference and did good. Con artists/cult leaders are very good at identifying what people want and making them think it is being given to them. Once JJ had people in his grasp, isolated from society, he had minions who would watch others. Any time someone would stray, they'd be confronted and accused of being harmful to the cult in some way or another. Made to feel guilty for straying. Anyone who is thinking of leaving, or trying to leave, will be surrounded by "love", not real love, but the illusion of love. They'll be physically engulfed, reassured, guarded, until they break down and submit. This is how he was able to convince people to poison their babies.
I know it may seem like there's no way you or anyone else would do something like poison your baby, and under normal circumstances, you wouldn't. However, trapped in a cult, your natural fear of rejection, guilt and losing that social bond your instincts crave will always get the better of you. This is also why people who are neuro-divergent (autistic, basically), don't end up in cults at all, or if they do end up in them, don't stay long. Cult leaders don't target these people because they don't have the same social instincts as the neurotypical, and are too hard to control. The economically challenged, disabled, minorities, those are the people cult leaders want. They are the most vulnerable and easily influenced. Cult leaders also like to get ahold of people with kids, because if they can brainwash the children, they can use the children as weapons to anchor the parents. Such as, "See how happy your child is? If you leave your child won't be happy anymore. You want your child to be happy right? I want that too. Stay and we can be happy together."
I hope all of that made sense!