Disclaimer: It's been a while since I studied islam, so take whatever I say with a giant grain of salt.
Thinkfree did Khomeni write that it was OK to marry infants or very young children and frot them until the reached the age of puberty? And then you can penetrate? I guess around the age of 9?
Afaik, Khomeini's view on the subject didn't diverge from the other marajae. Basically, it goes like this: The father has the right to accept marriage on behalf of a girl until she is considered rashida (mentally mature, basically) at which point she gets more than simple veto power over marriage proposals. If a girl is married before she is baligha (basically puberty, but in terms of marriage it's about sexual maturity and ability to engage in full intercourse) then her husband can engage in certain physical activities with her, not including penetrative sex. This is where you get into "thighing" and all that bullshit. Some people will try to fob you off that it's just "being affectionate", but it really has more in common with pedophilies sexually grooming children. It's very cringeworthy to remember that I bought into the excuses, that I would have even defended Mo's marriage to Aisha.
If so, where did you read this,
Various books I studied from and ulema I spoke to. Although, my little islamic library was recycled some time ago.
If so, what did he base this on? He can't just make up things on his own, they have to be based on scripture.
I only studied basic fiqh, I'm afraid. Ithna asheri shi'ism is all about taqleed, and junior students only really learn rules and their application, rather than ijtihad - which you can
start doing once you're ranked hujjat al-islam (run of the mill post-grad mullah) in modern shi'sim.