(i) Does Alan Moore respond adequately to charges of racist stereotyping and misogyny? I think so.
(ii) Can a white man write about black people and women? Of course. We assess how well he does it.
(iii) He can write about murder although he hasn't been murdered. Good point.
(iii) Are middle-aged superhero film fans unable to cope with reality? Alan Moore is right to raise this question. Some of us do try to address reality on different levels and also enjoy seeing it fantastically reflected in fantasy, sf and superheroes. I would like to see Superman addressing real world issues like war, corruption and pollution. Starting from an arbitrary year date, his history would soon diverge from ours, as happens in Watchmen and Marvelman.
(iv) Is Grant Morrison as bad as Alan Moore says? I don't know. I doubt that anyone can be that bad! I enjoyed Zenith, Animal Man and Supergods, although I felt that The Invisibles became incoherent. I have not kept up with Grant's DC continuity stuff because I have not kept up with DC continuity.