Ern was a bit startled by Zacharias' behaviour, but it didn't seem completely beyond normal. Upon being called "Virgin Boy", he was about to revert back to their days at Hogwarts and retort with a flustered protest, but he had used a professional tone previously and was determined to be professional. And plus, Ginny was still there and she spoke.
"I can't leave you here," Ernie said, not answering her question. "Not like this to leave you to something you'd regret. Even if he does deserve it." He wasn't even going to get into the argument about whether he thought Zacharias done Harry in or not.
Ern dug around in his robes pockets until he found a small bag and took a bit of Floo Powder, and after briefly explaining the situation, asked for the DMLE dispatcher to get an officer to Zacharias' address. They agreed with him and said that someone would promptly be over. "Someone will be over in a minute," he informed Ginny and took to leaning against a wall that wasn't obstructed by broken things.