There are people to blame and to be held accountable for the death of PC Harper.There but for the grace of God go I.
Not trying to be sanctimonious, but I strongly suspect this type of outburst is very common during/after inquests. By their nature, inquests are about unexpected/unexplained deaths, so usually concerning suicide or similar. The families will be going through heightened emotions and anger/bitterness will almost certainly be at the forefront of their thoughts or motivations.
PC Harper's wife and family have indeed been very dignified. But I don't think it's very helpful or compassionate to make that as a 'like for like' comparison. The woman is going through a hell that none of us can (and hopefully ever will) contemplate. I agree with a lot of the observations you made about her and no parent is perfect. But a parent that has lost their child is a shell of a person.
I don't think it's a fair comparison at all.