When dealing with a hostile ex wife two phrases will iron out many problems. "You may be right" and "How dare you!" Use "You may be right" often.This statement has no meaning other than "I heard you."
When her statments cross the line into abuse use "How dare you!" DO NOT ADD ANY OTHER WORDS! The point is to head off confrontation: Do not cause more. If the situation gets ugly, leave, take the kids if possible and go somewhere else.