Or otherwise, it might be better to recognize that we all live in a communal environment, and we need to put up with a little discomfort in order to function within society. In which case, neither overweight people nor people with children should be charged extra.
I recognize that I live in a communal enviroment, I also recognize that I paid for a specific 'allotment' of space whether that be in coach/business or F, if someone else wants to invade that space then we have a problem. As for the screaming baby, I will use my ear buds. What do you propose that I use to contain the POS on their side of the arm rest?