You're quite right Donuel, one should have the necessary skills in order to tackle an aggressive, fully-grown adult male. All I could do to disarm such a chap would be to knock him to the ground and firmly sit on him. He'd probably be crushed to death...

There was a case a couple of days ago of some poor lady on a UK train trying to breastfeed her tiny baby standing up, with two people's bicycles banging into her legs. Not one soul offered her their seat.