Though some of the arguments made here so far are pretty good, I think there's been one that's left out. And I think it's the main reason we shouldn't used "raped" in a general context:

There are a ton of terms and words used pejoratively that we, as a society, have stopped using because of the historical and present-day negativity.

It's not appropriate to casually use the n-word because it was historically used to demean and speak condescendingly to and about an entire race of human beings.

We no longer condone saying "that's gay" in a way that implies something is just "stupid" or "not cool" because it's unfair to associate a sexual preference in a broadly negative sense.

Also, we understand that using phrases like "he's such a girl" to explain weakness or insecurity actually serves to perpetuate a culture of gender inequality because we're implying that women, in a broader sense, are weaker and less secure than men.

Imagine how it would feel if you were black and your friends and colleagues used the n-word cavalierly around you.

Imagine how it would feel if you identified as gay and your friends and colleagues constantly said things like "why aren't you coming out tonight--don't be gay" or "dont play that game it's so gay."

Imagine how you would feel if you were a woman and your male friends and colleagues casually referred to each other's weaknesses using things like "don't order a girly drink" or "stop crying like a girl."

For the same reason, we don't want to use the term "rape", as doing so in such a casual manner can show disrespect. Imagine if you were a survivor of rape and your friends and colleagues casually said to you "you don't want to play me, I will rape you at Mario Kart" or "oh man, Team A raped Team B."

There are rape and assault victims out there. As a society, we understand that the use of the n-word, the pejorative use of the word "gay", and using "girl" to condescend or describe weaker qualities is unacceptable. Using "rape" is just as tasteless, especially when considering your audience might very well include someone who, unknown to you, might be a victim of this type of horrific crime.