I can only repeat that i am in no way motivated by spite. You will, no doubt carry on disbelieving that.
HEr parenting methods do actually have a bearing on a lot of htings that happen in my house too, you know. we may not see dh's children as often as we should, but they do come here sometimes. So yes, i do get an opinion, as does dh. merely on what happens here, and the differences between our methods, but it does all affect evereybody. They are also dh's children - so i assume his opinion is worth something in your world? Her methods as they impact on my children (in a watered down, knock-on "mum says it's ok, so I can do this" kind of way)are definitely something to do with me.
and, for the record, she does have opinions about my parenting, which she shares frequently with her children (and no they are not complimentary - one of them is that I have caused my dd's autism) and again, that has a knock on affect, and is something I disagree with (her sharing htis with my step-children, not her having opinions). Oh whoops, i appear to be "slagging her off" again. Better stop that. I am aware that nobody is perfect, and have never claimed that anyone is.
Yes, dh left her and the children, if you want to put it that way, in that he is the one who physically left the house and went to live elsewhere. short of insisting on sharing a house when the marriage has broken down (surely not advisable) or asking her to leave (which no doubt you would have vilified him for if that had been the case) I'm not sure what else you think should have happened? There was no-one else involved, if that is what oyu are implying. Their marriage was not working, they tried very hard, both of them, but they agreed that it was best if they split.
Dh got his new family a long time after he and his ex split up, and I have never said that his children should not have any feelings about it.