Not to get full-on conspiracy here but you're assuming airport security is for your (passengers) safety. The event that led to strict airport security was that planes were used to attack corporations (World Trade Center) and the government. Trains can't get hijacked and driven into the Pentagon so no one cares. But I admit this is a bleak view.

Doesn't number two work for literally anything you disagree with? Shops, hospitals, schools, bars, literally anything anywhere?

I've never even seen a weapon on a train. The worst I saw was some lady ranting about the anacondas, but she was mostly just annoying. She didn't hurt anybody.

So why does there need to be more safety stuff on intercity rail than on a subway? Oh wait, not that they get any ideas ...

You could make a more effective argument for that against buses. Trains at least need to stay on a track.