The development of the frontal lobe is somewhat researched (certainly not well research as neuroscience is quite new and changing rapidly), but saying from those data that someone under 25 years old can't fully understand the consequences of his action is nothing but speculative interpretation.
What we are talking here is morality. So go to a any 10 years old, describe what that teenager did and the reason he did it and ask the 10 years old if this behavior was good or bad. Again, try to learn a minimum about children moral development before thinking you know enough to have an opinion, because you really don't.
You think I have a trollish behavior? Tell me... If someone begins to argue with you that the sky is not blue, but red. You show him a lot of pictures with blue skies, but he simply discard them and continue to argue the sky is red. How will you react?