Citizen's arrest and he was resisting.....
I would not convict that guy even if he killed the offender and I would make his surviving family pay to fix his car.
A citizen has no protection against a false arrest. If you make a citizen's arrest and the person is not charged and found guilty you can be sued for false arrest. In some areas of the county the defendant could claim he was having a bad hair day and get the charges dismissed.
I am not sure what is allowed in a citizen's arrest situation regarding the suspect resisting arrest. He could argue the reasons for the attempted arrest were false and he was resisting an attempted kidnapping or assault being made under the guise of a citizen's arrest.
While it would upset anyone to be sure to see his car treated at the OP's car is treated there is very little one can do about it at the time -- without risking dire consequences -- other than to perhaps film the incident to add more evidence to the charges that would probably be filed against the suspect.