Filial piety is in general a virtue, as it is in conformity with natural law. Of course, killing a child to benefit his parents would be a terrible distortion; murdering one's child is never morally licit. Did Confucius endorse female infanticide? (I can't imagine Matteo Ricci admiring Confucius, if he did!)
You said that the philosophy of Confucius is "secular humanism," and the children are "brainiwashed" into it. This raises important questions:
(1) Do you distinguish between Natural Law, and Secular Humanism?
They do have this in common: that they do not make reference to a god who is the supreme lawgiver/judge, and their aim is "the good life" in strictly this-worldly terms.
Beyond this, I would argue that the terms are by no means synonymous, and in some ways contrasting. Natural Law is generally centered around the natural use of the bodily and mental faculties: ethically it is usually family-centered, communitarian, and expressed in customary and traditional practice.
Secular humanism is organized around liberty in pursuing personal fulfillment; it is individual-centered, it valorizes autonomy, and it is expressed in principles of legal rights.
(2) Brainwashing is a method that uses coercive and traumatic techniques such as drugs, sleep deprivation, exposure to heat and cold, hunger, and other physical duress to convince a person to abandon some of their basic beliefs and adopt the beliefs of the indoctrinator.
The term xi nao(Chinese, literally "to wash the brain") was first applied to methodologies of coercive persuasion which the Maoists used in the "reconstruction" of the so-called feudal thought patterns of Chinese citizens raised under prerevolutionary regimes. Thus it's historically linked to anti-Confucianism, not Confucianism.
I don't think that ordinary Chinese parents raising their children to be hard-working, honest, obedient, and respectful of parents, teachers, and elders, can accurately be charged with "brainwashing" their children. These are the ordinary aims of any patriarchal culture. You can find good examples of these principles in the Proverbs, and -- as I mentioned before --- in the Pauline Epistles.
Let me address your points one by one.
The "24 Filial Sons" is a historical textbook used for centuries in China to educate young children. It is not the work of Confucius, it is the work of Confucianists. It is not promoted by leaders today. However the values it promotes has permeated throughout Chinese culture for centuries.
I want to make it clear that Confucianism is not the same as reading Confucius. I actually have some respect for the man, not a lot mind you, but some. Confucianism as opposed to the writings of Confucius, is the aggretate collection of doctrines that have accumulated through centuries of Confucianists writings. When people say a return to Confucianism, they don't mean for everyone to just read Confucius, they mean for everyone to adopt this collective set of doctrines, and I'm here to tell you that most of these doctrines were establish by so-called scholars whose only interest is help the imperial regime strengthen their control of the people.
No, Confucius did not endorse female infanticide, but it is the natural outcome of a set of social values that considers woman inferior to men. It's akin to asking if Karl Marx endorsed the gulags. Of course not, but the inevitable consequences of trying to put Marxism into practice are the gulags. Which is why every Communist regime inevitably has some kind of gulag like institution.
Beyond female infanticide, even the women who aren't killed are mutilated. Can you imagine an adult woman with feet that are 3 inches long as a result of being bound from the age they are 4 or 5? That's what happened in China for a thousand years and was still in practice just less than 100 years ago. It was only encountering the West that caused the cessation of this mutilation.
Of course I distinguish between natural law and secular humanism. Confucianism is ultimately a form of secular humanism with one exception. The goal of the secular
humanism that you are talking about is meant to achieve individual fulfillment. Whereas the Confucian ideaology is all about the collective, personified by the ruler. It says little about Justice, only "Loyalty". For example, Confucius himself said that if the parent commits a crime, it is wrong for the son to testify against him, but the son's duty to help cover up for his parent. Translated onto the political scene this equates to: the subject should not care about the whether the ruler is doing justice, it is the subject's duty to defend his ruler regardless, because "Loyalty" is the ultimate good, not Justice.
This is partially why Communism was so successful in seducing the population of China, because for centuries they have been prepared by Confucianism. The concept of individual rights was foreign to China until they encountered the West. The idea that all men are equal is also an anathema. Which is why the idea that Confucianism prepares the people for Christianity is ABSURD.
As for brainwashing. I am talking about a system of indoctrination, both social and through schools, that begin at a very young age. This is why it is very difficult for a Chinese person to break free from that type of thinking, because he never encounters any competing set of values.
"I don't think that ordinary Chinese parents raising their children to be hard-working, honest, obedient, and respectful of parents, teachers, and elders, can accurately be charged with "brainwashing" their children."
If that were all it was, then I'd agree with you. But like I have written above, the ultimate goal of creating obedient children isn't so that they'll respect their parents, it is that obedient children will make obedient subjects. So they don't just learn to respect their parents, they learn this entire set of values, much of it noxious.
Confucius was an advisor to the rulers of his age. Most of his writings were mostly a set of instructions and advice to the King (he lived before China had emperors) about how to rule, and what set of values to promote in the people so the ruler can best maintain his rule. In that respect you should think of it akin to The Prince by Machiavelli.