What is the Sharia ruling on a father filing a false lawsuit against his son, who defended his mother?

"We pray to Allah to heal your father. If a father unjustly oppresses his wife, and the son prevents him from doing so to protect his mother without causing harm, then there is no sin in that. This is because preventing a parent from injustice and forbidding evil is not an act of disobedience; rather, it is an act of righteousness. As the Prophet, peace and blessings be upon him, said: 'Help your brother, whether he is an oppressor or oppressed.' They asked: 'O Messenger of Allah, this is the oppressed, but how do we help the oppressor?' He said: 'You prevent him from oppression.' However, gentleness, kindness, and wisdom must be used when dealing with parents. If the father is mentally ill and behaves inappropriately, there is no sin in preventing him from these actions with wisdom and gentleness, while taking into account his psychological state and attempting to treat him."