Not helpful to the OP, but this sort of passive aggressive FB post really irritates me. We get a lot on my local page, too.
'I just want to thank the person who blocked me in by parking over my drive.'
'I hope the woman who told my daughter off for nearly knocking her over in the bus station is happy that she upset her.'
'I'm sure the parents of the boys who play loudly in the street when my mother is ill are very proud. And so on.'
The pointless complaints are bad enough, but why pretend to be thanking people or to claim to hope that they are proud? Everyone knows it's insincere, so it really doesn't help the case, and there is no point in posting on FB instead of complaining to the people concerned at the time.
In the OP's case, the post is quite threatening, and equally pointless, as the only people who can 'take the car off the road' are the police and/or courts, and they can't act on the sayso of a random FB poster. I think I would ask the person who sent it where it was posted, and then contact the group admin and ask for it to be removed.