His analogy is perfectly consistent. There are laws prohibiting minors from purchasing alchoholic drinks. In the same way, porn can be restricted from minors. He is just saying that there needs to be strict enforcement of a law against porn to protect minors.
I guess your argument is that there is no need for a law against alchoholic drinks since there is common sense to not give alchohol to minors and for minors to not drink alchohol.
But the existence of laws regulating alchoholic drinks purchase suggests that common sense is not enough and laws need to be created for it.
The concept of liberty is how we rein in this dark tendency.
(I use 'you' as a generality, not you the poster ;-) )
OP didn't say ban all porn, but it should be more tightly regulated and its consumption has proven to be damaging.
Also, I believe there are a number of non-porn sexual education resources, which should stay available.
However, note that the current crackdown on porn isn't about underage consumers, it's about consumption in general. Apple isn't asking for age verification, they are banning adult content completely.
OP said Apple's stance is reasonable and Apple is pretty close to saying "ban all porn".