I understand your perspective and yes, it is annoying that they resent the fact that their child isn't gifted. But I am too lucky with my kid that I will not fault them. I do not know what I would do in their place.
And I did not mean from a SES that they come from. I am talking about the average IQ scale that they come from. What they could achieve isn't an option for their kid. And you really don't know how much they have to give their kids as many people are living just within their means.
I just wanted to add the perspective that I am glad I do not have to redshirt but I do not know what I would do if I were them.