So your assertion is that she couldn't have been raped because she didn't fight back hard enough?

No, that isn't their assertion.

Their assertion is that fisting a person while also masturbating is not an "on the fly" action.

That would take planning and restraints, especially if the fistee isn't a voluntary one.

Meaning, that unless they were restrained against their will, they would have had both hands free to do...well, anything.

I'd wager there aren't many women out there that are going to have an entire adult human fist forcibly shoved into their vagina while their assaulter also masturbates onto their face without putting up some sort of fuss.