I feel sad for him, but even more so for the children. When an ex-spouse interferes with children having a normal relationship with their other parent, in the long run it hurts the children more than her intended target. Whether the interference is active ("Remember what they said about apostates at the last assembly?") or passive-aggressive ("If you don't really want to see him, that's okay honey!"), this is emotional abuse--what they call parental alienation syndrome.
With her appearing to be beyond the reach of common sense, reason and civil behavior, doing anuthing about this menas hiring a lawyer, probably going to mediation or the family court (several times), and dealing the time, hassle and EXPEN$E of doing all that. But if your husband does nothing, she gets her way by default. She knows this, and is using it to her advantage.
For the sake of the children as well as your husbands, I hope you can restore some semblance of a normal family relationship with the children.