I can fully understand where both sides are coming from. Honestly, if he's watched porn at all, he's gotten insecure about his size. Hell i think that's how most of us got here (aside from the guys who saw their EQ slipping)
The point is, we all place a great deal of our happiness in our penises. Not just in size, but in function as well. An early start to PE would help him later on in life to dodge the bullets of soggy penis (low EQ problems), PreE, and any.. ANY size deficiencies he MAY have felt at any point in time.
Sure he can be reassured by his lovers, but at some point, he's going to feel jipped in the penis department unless he's absolutely positive he's got a monster dangling from his hips.
I didn't know I was hung before PE. I spent a LOT of time bettering myself (in sexual techniques and life stability) because I assumed I had a smaller penis. I'm still not absolutely sure I'm hung. My confidence is still in what I've done in the absence of having the confidence of a big peen. Does it help now that I have a bigger willie? It helps all kinds of ways. If he was able to give his son the chance to create confidence that's unbridled, and his son has the ability to control that confidence, more power to him, i say.
My thing is, You can tell someone about PE, but if they're ABSOLUTELY certain they're happy with themselves, they'll look at the time it takes to enlarge your penis and say "forget that sh*t" and go on without a second thought.