Television

That's like saying drinking water can be bad. It's technically true, but not really relevant to this context.

Let the kids family, friends, directors, whatever people are actually involved in those children's lives handle the constructive criticism. The scrutiny these children face is monumental already. There's no reason for some rando online to give unsolicited acting advice to child actors, and we both know that's not even remotely how the vast majority of armchair movie critics are going to express their opinions.