Mainly, as one commenter said, Militia members want to convey that the incident was serious and was "not a prank."
Below is a photo provided by Gene Tozzi, the Mercury's captain, of the boat when it was found on Tuesday afternoon.

The good news is that it seems the boat will be able to participate in the burning of Kingston this weekend.
The perpetrator(s) is/are still at large/delusional.