How can one deal with a father who mistreats his dutiful son, attacks people of religion and righteousness, encourages his children to commit sins, and is misunderstood by the father?

If the father is abusive and reciprocates kindness with ill-treatment, then your dutifulness towards him is a great righteous deed, and his ill-treatment will not harm you. "If you are as you say, then it is as if you are feeding them hot ashes, and you will continue to have a supporter from Allah against them as long as you remain in that state." We draw attention to the fact that the obligatory spending on the wife and children takes precedence over spending on parents. The greatest dutifulness towards your father is to advise him, guide him to repentance, and pray for his guidance. If there is a legitimate benefit for the parents in estranging oneself from them, then there is no harm in that, while continuing to maintain ties with them through what is obligatory upon you in terms of financial support and the like.