On sexing(up) the detective

I have been watching again, the spate of Agatha Christie film and TV adaptions filmed over the last few years A number of things really annoy me about them even though I do enjoy them, abet in a slightly irritated fashion. In a misguided sense that these stories will be more dynamic, they add a lot of extraneous plot elements and sexual subplots. It not the sexuality per se I object to, it is the dubious fit these sometimes have with the original storyline and even more outrageous, the hamfisted alterations of murderers, motives and denouements. Writers for film argue that the transference of a story to film necessitates changes to provide dramatic tension etc.
However, guys I have to say Agatha Christie was a far better writer than your scriptwriters and messing with her works is often not only arrogant, disrespectful but unjustifiable in  many cases.
1) "Sittaford mystery". Can you justify calling this an Agatha Christie story when you changed a) the motive b) the murderer C) added Miss Marple to the plot when she wasn't in the story? Can we consider this a, dare I say it, cynical desire to cash in Agatha's immense popularity while disregarding her plot.
2)"The body in the library".a) Changed murderer b) Introduced lesbian love affair motive. I happy to see depictions of non-hetero characters but the disturbing tendency of the scriptwriters to define them as murderers (see also "Cards on the table" where the murderer(s) have been altered to the gay doctor and Miss Dawes)suggests 50's pulp fiction exploitation rather than a sympathetic image
3)In "Murder in the vicarage". Miss Marple as played by Geraldine McEwan empathised with murderer whose motive has been a desire to marry her lover that she has been having an adulterous affair with, and we are shown through flashback Miss Marple's own adulterous relationship with a soldier in www1. Well, this of course did not occur in the book, which came out in 1930 (which would make Miss Marple an unlikely age for a youthful affair in 1918). Some might see this addition as grossly insensitive to Agatha Christie who suffered a breakdown from her own husbands affair. Sorry for the long post next time I rave on I will add a link with the arguments in.
4) "Nemesis" is the maddest of the lot. This was a quite sensitive story about thwarted would be maternal attachment and the evil of feeling that we can own a human and hence can destroy them (Think of real life parents who kill their children in murder/suicide events ). The writer/producers who thought up the dramatic treatment for the tele film should be forced to sit a class on ethical use of source material. Their nemesis is a mad gothic tale worthy of Radcliffe or Lewis, deranged nuns grapple with wounded enemy soldiers in a storyline so far removed from Christies' they share little more than a title.