And what if the street cleaner jammed his shovel into your instep? What if a dog-walker whipped the chain off his mutt and started swinging it at head height?
Hoodies with crowbars is a silly suggestion, yes, and I'm sure it wasn't serious, but that's not to say that the vandalism (and that's what it is) of Southern and TfL in this instance should be ignored and blithely accepted.
I'm more bothered about the gate being shut after the station is no longer manned than I am about it being shut when it will prevent fare-dodging. The prevention of fare-dodging is a legitimate aim, and while this is a clumsy way of going about it, I wouldn't get too worked up on that front.
The closure after the end of staffing hours, though, is a different matter. It will produce no revenue whatever, and is nothing more than a gratuitous inconvenience to passengers. So some form of action is appropriate. Walk up the steps when the gate is closed and tie stuff to the gate. I don't know. Something.