There's also a difference between fapping to and grooming a 15 year old. The moral argument is based on mental maturity of a minor, not the actual age number or physical body. With actual children and not minors it calls into question the mental health of the individual. Teenagers at least, by high school, have adult bodies.
Make no mistake, back in the good old days, there used to be lots of pron that featured cheerleaders, jocks, nerds, teachers, and school uniforms. It's not because everyone secretly wanted to bang high schoolers, it's probably some psychological roleplay in their mind to something they can relate to or a period in their lives where they were curious sexually. Flamenco jacking it to school girl anime doesn't make him a pedo where even discussing lolicon should into place.
but I didn't watch the full conversation, just saw what a shitshow the talk of lolicon was.