Regarding verbal abuse on call to my father who is headmaster in government school.

Actually we were planning our sister marriage to a boy. But the boy later felt not a good and suitable for marriage with my sister. One day he came to my house from long distance from his home to defame my sister intensionally (when he got to know that we know his reality fo drinking and may bad habits and we will not anymore gonna marry with him). But he couldn't succeed as in mid night because when he came to my house rooftop and call my sister on roof by telling him lie that your voice is not coming come to roof top for better voice while he was already on my roof top reached from back side of the house. Now, one of his friend were waiting on road with bicycle for him when this boy came to my house room top. Suddenly, police came to road and caught his friend standing and waiting for the boy. Police ask him about him on road on night but he couldn't answer anything..also in discussion with police he tell that one of his friend also there. Police call the boy immediately and said to come there immediately. The boy returned to road to his friend on police phone call. And police take both boy and his friend to police station. And within one day matter solved. Boy reached to his house. Now his maternal uncle called to my father(very respected and honest government teacher) and started abusing him very badly. My father couldn't say anything and didn't tell anyone in home. Now we come to know about this. What should I do for his vernal abuse to my father by his maternal uncle.