Ah, I see now. His parents have no real 'loving type of relationship' with you where 'trust and respect and etc. reside', but they took it upon themselves to start telling you how to behave, rear your children, etc. That was not a very wise decision on their part and a horrible way to start out a relationship. Sad. And sorry to hear you had to endure that.
In cases like that, family, no family, strangers, etc. I take what is said with a grain of salt. Unless I know someone's character, or have a 'love/trust' relationship with them, I question motive. I have to know I am being constructively criticized out of love, true concern, etc. That is just the wise thing to do according to what I believe. My spirituality comes into play too as I do not take advice that goes against God's Word, to the best of my knowledge of course.