Northern Ireland is not happy with Twenty One Pilots right now. Or at least the political party Traditional Unionist Voice (of course it's political. Everything is these days). According to this article from AltPress, JimAllister, the party's head, said this:
“Balaclavas are the stock-in-trade images of terrorism in this part of the world,” Allister said. “So to don them at this sort of event inevitably has the consequence of sanitising or glamorising that with which they are associated in this part of the world, namely terrorism.”
“Whatever they thought they were doing, this is hardly the sort of imagery that Belfast needs. Balaclavas still speak loudly in Northern Ireland of the evils of terrorism, with many still struggling to cope with the devastation and murder wrought by balaclava-clad killers.
“I would be very surprised if nobody associated with this operation has any knowledge of the Troubles, which has been beamed around the world for decades.”
Here's video of the performance in question. This is, of course, par for the course for a TOP concert.