I strongly disagree with Harry's point of view but I think he truly believes that William allowed his staff to plant negative stories about Meghan - the first being the row over bridesmaids dresses. They feel that William and Catherine were jealous of Meghan and were trying to make her unpopular. I think they believe that William and Catherine should apologize for that.
Some people on this board will agree with Meghan and Harry, but I doubt that anyone besides William knows. There would have been other witnesses at fitting, including staff and the mothers of the other girls. Regardless, they have blown that one story out of proportion. It only got "legs" when other allegations that Meghan was difficult surfaced. Again, I don't think William and/or Catherine were behind these stories, we know that Valentine Low actually witnesses Meghan snapping at her staff.
I'm sure that William and Catherine did not handle everything perfectly but Harry and Meghan have smeared them, along with most of the rest of the family as racist. That more than balances out any perceived wrongs that William and Catherine committed. Also, we now know that at the same time, Meghan was feeding negative information about Catherine to Omid Scobie, so they really don't have any room to criticize.
I don't understand why Harry thinks that the family should have been more proactive in caring for Meghan's mental health. Harry admitted that he didn't ask his family for help and I still don't understand why two people in their mid-thirties, with their own doctors and staff, needed his family's help to arrange counselling.
Harry's anger with Charles is probably more complicated. Obviously, Harry is still struggling with Diana's death and blames Charles for her unhappiness. At the same time, Harry loves his father. Harry is just going to have to accept that Charles can't change the past and learn to let go. Until Harry does, he will never be truly happy.
It's also obvious that Harry resents Charles lack of support for the HIHO and the refusal to pay for their security. In my opinion, the HIHO would have consisted of Harry keeping his military patronages and appearing whenever they wanted. It might have worked if Harry and Meghan had made money with a few acting jobs and sitting on uncontroversial corporate boards but that type of income would probably not maintain their current lifestyle.
I'm going back and forth about whether they will show up at the coronation. I am sure Charles will issue the invitation and I think the way Andrew was treated at Christmas will be the blueprint. If they attend, they will not have an official role but as Charles' son and daughter-in-law, they will have good seats. I tend to think William and Catherine will be polite but if the book is too nasty, all bets are off.