I don't get the connection. I would think that at least some homosexual activists -- the ones in NAMBLA -- would embrace that position.
I wouldn't state in broad terms that it's an "arbitrary and useless concept." A six-year-old should not be engaged in sexual activity, driving a car, buying liquor, working full time or signing contracts. Puberty happens, and children gain maturity and wisdom with time.
The ages -- age of consent, 16 to drive, 18 for most definitions of adulthood, 21 to drink -- are wholly arbitrary. There re certainly some 16-year-olds who are more mature and ready for responsibility than some 26-year-olds. But when it becomes a matter of law, there needs to be a clear enough line that folks can understand the law and obey it.
In the olden days, people older than 14 or 14 were adults and got married.
And children under 6 worked in sweatshops and were basically bought and sold; sexual exploitation of children was rarely if ever reported; most people were illiterate; and the life expectancy was about 30.
Working in sweatshops was better than what was there before, working on the farm. And illiteracy is forced upon children now with this look/say -- whole language garbage taught in schools.