The reason most players who get knocked out is through head collisions, 50/50 collisions do you only book the one left standing?
Accidents happen, not everything that occurs on a football pitch is intentional.
The point of dangerous play is exactly that it isn't intentional. It's just something that in general is dangerous, likely to cause serious injuries and therefore shouldn't be done at all. Like raising your boot to head height or running at full pelt towards a goalkeeper with no chance to challenge for the ball.
I'm 100% certain Romelu didn't want to barge into him and as a striker he had to do what he did, but from a neutral point of view that doesn't make his actions any less dangerous. So much so that he himself got injured as a result. Again, what is dangerous play if something that injures both players isn't?
It was an unfortunate incident, that's all.
And of course Friend was bad but not outrageously bad, certainly not worth-a-disciplinary-hearing-and-a-fine bad. It wasn't even his worst game for us.