Smum- Sorry that was written really quickly - I meant the woman was silly and clearly needs professional help. It is very sad for the boy.
It wasn't always like that for us though. The girls have been submitted to very damaging behaviour (parental alienation) from their mother- we had to go to mediation to put a stop to it. Very lucky in our case, her partner was on board with us. he was also sick of hearing her badmouth DH !
In all fairness, she took it on the chin and changed- the girls have been much happier since. Her partner won't allow it because he finds it equally damaging for the children they have together to hear such negative things.
The one thing we kept from the mediators ( they were excellent I must say) was this- we are Project Managers and must work together at managing our children's life in the best way we can. Working from that viewpoint really works for us.
The children will never judge you as a Husband/Wife/Partner, they will judge you as the parent you are to them.