This is clearly bad form; but at this point, we don’t know if either the father or the daughter have it, or are carrying it, so this probably will turn out to be nothing.
That’s the whole point of quarantine.
It’ not just for the infected, it’s for those who MAY be infected too.
And the dad should be legally liable for the costs of cleaning the venue and anywhere else he shouldn’t have been.
Also the medical expenses of anyone who may get sick as a result of his behavior.