“If these are trained terrorists, you won’t have a chance to fire back. You’ll never see them.”
That works the other way, too.
With trained weapon carriers, the terrorist won’t have a chance to set up a terrorist act. He’ll never see them coming.
One of my Israeli coworkers was waiting for a bus in Tel Aviv. At the stop before his, a fat Arab woman got on. As she made her way to the center of the bus, she triggered her bomb. It flattened the bus, killing everyone on board. That is a terror attack. There will be nothing to shoot at.