I could have also framed it to make it seem far creepier

I'll put it simply: if someone asks me about my kids, neither to be polite nor because they care, but because they want to change the way I behave, then they're (in most cases) being manipulative and insincere. While perhaps they're not wronging me, per se, it's certainly not something that speaks well of them, ethically speaking. If you find this controversial, then you surprise me.

It would be bad advice, I think, to encourage people to use positive reinforcement on others when their ignorance is necessary for it to be effective. Not just practically bad advice, as people are pretty good at picking up on fake friendliness. But full stop ethically damaging advice, if taken seriously. I'm not saying that every such case is going to be unethical, but I'm not in the business of lawlike ethical principles anyway.

That said, you seem to be going from that claim to the implicit claim that they are bad by virtue of depending on my ignorance. That's less clear to me.

No, what I said was that behaviors which depend on someone's ignorance for their effectiveness are often also bad behaviors. I didn't say anything one way or the other about a stricter relation between the two properties, but I'll say now that I don't think they're unrelated.