Patience is a virtue, and Jesus said to love those that spitefully use us.
It's hard - probably one of the hardest things there is - when the spiteful users are parents. This probably is your own Gethsemane, where you are pleading for the cup to be taken from you. It can't be, so I advise you to set inviolable boundaries - "acceptable minimums" that will result in temporary withdrawal if crossed.
Say to them something like:
"We love and always will honor you, but we can't allow you to hurt us by doing (or saying) _____________. We will never withdraw from you if you don't do (or say) _____________, but if you do we simply won't be able to see you or talk with you for _______________ (an established time frame)."
After saying it, stick to it. They really do love you, even if they are messed up in how they express it and need to repent in this particular instance. It might take a long time, but they will get the message - and even if they don't, you will be a better person for taking a calm, measured, loving approach.