I'm one of those friends so I have to throw my online onpinion on this. I personally belive that if he was so strong why when they had the ability to did they never go super saiyan 2 or 3 for that matter. It just doesn't make sense in my opinion. Look at the bojack movie Gohan went SS2 to kill him but when he's older he doesn't even give it a tought. Overall I would say that broli's power isn't infinite if it says it is. its just a flaw by the creators of the movies.