I’d say the quotes above show he absolutely believes children are capable of consent. Why else would he use phrases like
“it’s fine so long as nobody is coerced” (as if there are any situations where an adult can have sex with a child without there being coercion)
“willing participation in pedophilia” (children can’t consent to sex!)
“the arguments [against having sex with children] seem to be based on cases that aren’t voluntary” (None of them are voluntary! CHILDREN CANNOT CONSENT!)
It doesn’t mean he supports it.
He explicitly said it should be legal, and also alluded that parents are just prudish if they don’t want their children to be having sex. It’s very clear he supports it.
You’ll be able to find this stuff in the articles that went around when he was pressured to resign from the FSF and from his role at MIT. It’s primarily quotes from him on his own site, stallman.org.