Maybe he does regret it but he made the choice to go on air and do that which will have had an impact on his children and their mother. Diana also made that choice and to me it looks like neither thought about how it may affect their children seeing their parents doing that to each other for the public to see.
Maybe Archie won't like it but we won't know until then.
Again, I don't see what the point is in talking about things which happened a quarter of a century ago. Charles and Di gave one interview each, and quickly regretted it. Harry has been running his mouth for months, with no end in sight.
I think doing interviews talking about your affairs (while still married) and talking about the negative effect your family have had on your mental health are two different things.
That sounds like a fairly arbitrary distinction to me.
What good is going to come out of Harry constantly slagging off his family in public? If his family damaged his 'mental health', then surely it's best to discuss it with them, or with a therapist? How is being bitter about them in front of the world going to help anyone?
Would you be happy if a family member took to the airwaves, or even to Facebook, to claim that you damaged their 'mental health'?