Asked specifically if police will act on this today, Hishammuddin Hussein said: "Yes, yes, yes."
He said no one will get special treatment and that the government has made this stand clear.
"I've already told (the police) to treat Pemuda (Umno Youth) the same. Nobody is above the law," he said.
The youths allegedly threatened to burn down the building which is in the same row as a police station.
According to PKR secretary general Saifuddin Nasution, who rushed to scene at 11pm, the youths were also wearing Patriot t-shirts.
Umno Youth has plans to hold its own rally on July 9 - dubbed the Patriot rally - to defy Bersih 2.0's call for electoral reform.
The Election Commission (EC) has offered to meet Bersih 2.0 as long as it calls off the demonstration, but the offer has been rejected.
Bersih 2.0 said it has tried to engage the EC, but to no avail, over the past four years.