I don't understand how what you've answered changes the fact that Stallman openly implied with his opinion that absence of consent (rape) makes a sexual relation unethical and bad.
Stallman is against rape, and arguing that criticizing the ambiguous use of a term in a certain context (sexual assault) makes he somehow pro-rape seems unreasonable (but I'm open to explanations I didn't consider, if you wish to try).
In general, if you have any sources for your claims feel free to share them (I can't find any sources quoting stallman saying anything that vaguely resembles a pro-rape argument, and I've gone through most comments in the section).
More specifically, Stallman didn't ever say that raping children doesn't harm them, if your definition of rape is sex without consent (that's the legal definition in my country). He said that if you have consensual sex with a minor then that may not be harmful for him/her (the fact that this is not "raping children" follows from the very definition of rape).
I'm trying to leave my feelings aside but you really seem to be misquoting Stallman to try to make a point. I really hope I'm wrong about this so I'm genuinely curious about what did you mean when you said he stated that "raping children doesn't harm them".
In this specific example he is not against rape because he is trying to redefine rape to make his colloeague look less guilty of rape.