OK, what the hell has happened to the Brits?

Cub Driver wrote:

I was driving home from Cannon Mountain yesterday afternoon, and
listening to NRP (National Partisan Radio) as I went. The subject of
air marshals came up. The Talking Head was a London-based security
consultant. He said in effect:

"You don't want guns on aircraft at 30,000 feet. The air marshals have
frangible bullets, of course. But what's to stop the terrorist from
getting into a shootout with the air marshal? The terrorist won't have
frangible bullets. Then you have the specter of a bullet piercing the
airplane's skin, explosion decompression and all that entails, even
unto passengers being sucked out of the aircraft."

The statement, of course, went unchallenged by the host.

What would you challenge? The fact that you don't want guns on board?
The possibility of explosive decompression?

I have seen it said that a bullet hole through the skin would not
cause explosive decompression. I can believe that is true if it is a
small hole, from relatively perpendicular to the skin. What if the
bullet was at a shallow angle to the skin however, as if it had been
fired along the cabin? Then I would imagine the hole would be more
like a long tear, and explosive decompression seems more likely. There
is a lot of pressure there, remember Comets, JAL, Aloha airlines etc.