TD, to the average "jo public", trainers doesnt mean trail trainers.
Fact is, you are giving a very irresponsible view of things. A walk up the pony track in the summer might be OK with trainers 9/10 times. But if a weather front moves in, it could soon become quite different. I wouldnt do it.
Fact is, these four were absolutely blinking idiots. They should be condemned as such. With your experience of hill walking going on about "victim shaming" blah blah you probably ought to be saying "dont do this, it is stupid, you may die". But we all know you'd rather make a point than ever back down.
(And I do know a little bit about hill-walking - I reckon I bagged my first munro about 30 years ago. With ALL the right equipment and the knowledge of how to use it!).
I'm out now.