Actually I don't entirely disagree with him. The warnings present at that time clearly weren't overly sufficient as two people died. Even if the girls were foolish, something like that shouldn't really have been able to have happened, especially when the problem had already been identified by national rail and it's not something overly burdensome to have accomplished.
Never underestimate people's ability to be stupid. No matter how good your safety systems are, there will always be somebody who is stupid enough to think they know better, and end up causing something like this to happen.
Just because someone was stupid enough to break the system, is not reason to declare the system inadequate.