Harley may have wanted them to rush in, but the Bat wanted to get a better idea of where the damn dogs, cats, animals were.
"Head in; watch your six." The command was given over the comms; the Bat had to believe that the Canary was where she should be. Stepping carefully over the glass, even though some of it had to be kicked in, gun held down for now, the Bat went in. As far as the Bat could tell there were no humans, save for the two of them, that would get in the way, just the animals. On the one hand, the Bat was glad that the Joker's girlfriend wasn't around; on the other, getting her into some secure location would have been a good idea.
The Bat's head jerked at the yowl, but it was further back in the store. No, the Canary would have to take care of the yowler. The Bat had to put down the two causing more chaos and destruction than seemed possible for animals.