I seriously believe the demographic of /r/leagueoflegends to be 10 or so years of age under that of the average redditor. Let me explain why rape as a metaphor is a terrible descriptor for anyone who is defending it, and show why it is essentially not used out of the gaming community (i.e. a predominately male one).

Try telling an adult that they're "fucked" or that you want to "kill" them. While the first statement contains a profanity and the second a heinous wish upon them, we can probably brush off these statements relatively easily. That is because there is no controversy whatever surrounding the actual meaning of "fucked" or "kill". It becomes a easy matter then to distinguish between someone throwing the term around figuratively or literally; i.e. distinguish between a joking and serious usage.

I dare you now to say I "raped" XXX to an adult. Whether you use it figuratively (as what happens 99% of the time in the gaming community) or literally, you are always going to unsettle everyone around you and will probably receive some sort of rebuttal. Why is this? It is because rape is controversial in that not everyone will understand it as concretely as saying someone is "fucked" or that you want to "kill" someone. An example is the typical series of comments you will see in /r/adviceanimals regarding rape that will generally invoke the following arguments in one way or another: "Women should not wear sexy clothing/put themselves at risk going to a dangerous location because it invites rapists" or "women who claim false rape should be punished as much as the man who served a sentence". These are completely misconstrued perceptions of rape as statistically, the incidents resulting from the case cited by the redditors is probably under 20% of all actual rape cases. More than 80 percent of victims will know their attacker. For the second argument which is more of an opinion, the premise is morally and legally compelling but it completely distracts from the suffering of actual victims. The woman who cries rape is such a statistically anomaly from the population of actual victims and it really pressures the victims into silence, evinced by the number of unreported cases. I'm not going to touch on rape that occurs outside of America and for that matter other 1st world countries because it only gets worse.

tl;dr It's relatively better to say that "I fucked ur mum" or "I'm going to rip your fucking head off" than to say "X raped Z" because you know either the guy is facetious(joking) or serious in the first case but in the second case, you have no idea if the guy is facetious with the correct understanding of rape, facetious with the wrong understanding of rape, and being serious because so many people don't understand what rape is; otherwise it wouldn't be happening so much.

Edit: another example