Earlier quoted context omitted.
Which always makes me wonder, what is the extend of the child pornography problem? How big is the nail compared to the proposed hammer? If I had to guess, I would guess this is hammer affecting 80+ % of the population to go after a group constituting a fraction of a percent of the population.
That's a very good question: how to quantify child suffering to one of the worst crimes imaginable? I am not saying I am for or against. I am just trying to point how really difficult is to quantify both sides of the equation.
Also the decision is not a dichotomy between complete surveillance of all communication and doing nothing at all, there are other measures that can be taken additionally or alternatively. So the proper measure is the additional utility of banning end-to-end encryption over all the other things you can reasonably do, not over not doing anything at all.