I assume your parents honestly believed it was right and unquestioned. How could they then present a balance without questioning their own beliefs, and why should they?
Is it correct to teach two sides to theft or murder? We believe theft and murder are wrong and so we dont teach both sides and yet there are two sides as many cultures operated on differnt values in the past.
My parents believed extra marital sex was wrong (not from religious reasons but from logic and common sense) so they taught me that value. Why teach me an alternative one which they had found to be harmful and destructive compared with a faithful lifelong relationship. Were they right or wrong? It has worked exceptionally well for me. My wife and i have been faithful to each other for over 40 years, and as a result have a very strong and loving relationship. I see the great harm and angst caused by extra marital sex, yet some people see no wrong or harm in it. They have different values and attitudes and perhaps dont value loyalty duty etc as much as danger and excitement. ( I t is more complex than this of course but tha tis my point, we can only teach that which is right and work s for us)
In most people belief and morality, values and ethics, are indivisible. We hold values via beliefs. In some people those beliefs are religious In others they are cultutral or personal. Your parents probably had to teach you religion to pass on their values because, for them, their values, ethics and moralities, were tied to their religious/spiritual beliefs..