They don't really need to do any explaining. The baron led a company of mercenaries, of ill reputation, to a count's mansion. It's only natural the count's daughter residing there would defend herself. The only caveat is how much work the baron had done to transfer himself the title and who's backing him. If the king had already signed the paper, then the baron (future count) could be viewed as having the right to seize the mansion, by force if necessary.