Because you have decided to justify your actions, tends to suggest that you know it wasn't the wisest thing to do - very kind and helpful, but still not the wisest act of the day you could have done.
The actions of the camper van driver have highlighted the dangers that other ill-informed drivers who are unaware of the situation ahead of them can pose to acts of heroism without the correct rearward protection.
Most motorway drivers only seem to react to blue lights ahead of them, less so to amber lights (and also matrix), and they wouldn't have had a clue as to what was going on with the hgv.
Best left to the professionals (Highways Agency questionable? Police - definitely)
I justified it because it was called into question.
In the exact same situation, I have done it before and would do it again. In other circumstances I would make the decision on merit.
Calculated decision making is something I get to do most days at work. I'll give you two examples of situations where the choices are the worst case or the slightly less worst case and let you ponder how you would respond in each situation.
1. Coming into land, a couple of minutes out and strapped in. Toilet smoke alarm sounds.
Do you a) get up, silence the alarm and investigate the cause; or b) sit there wondering?
2. Strapped in and heading to the runway to take off. As the aircraft turns onto the runway you look down the aisle and see two trolleys break free.
Do you a) sit and watch them bounce their way down the cabin as you take off; or b) get out of your seat and pin them in place with your arm whilst bracing yourself against the bulkhead?
One situation was just poor timing, tother totally avoidable but happened nevertheless. Both are the immediate situation and have further decisions and potential consequences as a result of which choice you make.
I know what I did in each situation and would make the same decision in each case, although the avoidable situation is now less likely to happen to me again.
Having had a moment to reflect, I wonder if you would still drive past without a second thought or would perhaps actually, or at least consider the possibility, do something about it.