Rape is not material for jokes, irony, or metaphor. Rape is the worst thing that a person can experience, and minor upsets like buying something that is overpriced or losing a game are absolutely nothing like it. Even more serious violations like having one's diary read without consent or being pressured to alter one's art are not at all the same. Inanimate objects such as a car, the earth, or a bank account cannot experience rape. Rape is a stripping of one's basic rights, a complete and utter denial of one's humanness. It's not okay to refer to rape in any manner other than with great awareness of the horror and the tragedy that it encompasses. In using it ironically/jokingly/metaphorically you are not being clever with words, you are not being funny, you are not simply expressing a feeling of violation; you are trivializing the suffering of victims and encouraging acceptance of the act, no matter how subtly.
To know if use of the word 'rape' is an acceptable metaphor, consider whether you would rather literally experience rape or experience what you are currently experiencing. Then, if you have never experienced being sexually violated, realize that you do not know the answer to that question and you have no right to judge other people's experience as being the same as your own.
Rape is NOT like any other violation. Rape is not a synonym for any-old-violation. Rape refers to the sexual violation of someone's body.
Casual use of the word rape (or molest, used in a sexual connotation such as 'so-n-so is molestable') makes it more acceptable to joke about the actual act, which in turn makes the actual act seem less horrific and annihilating, more acceptable. Words have power, and how we use them affects the world around us.
I once was working as a cashier when someone came up to me and in the friendliest tone said, "I'm going to rape you--
r drawer" (referring to paying for something small with a hundred) -- ze did not include the pause but I felt it like that. I was so in shock and triggered I couldn't respond. Nowadays I'd have Something To Say. I think ze was actually expecting me to laugh, and seemed to realize that ze had made a mistake when my smile dropped and I froze. (later I wished I had been able to speak because I think that was a moment when the right words could have made a huge change -- I only hope that my wordless reaction said what I couldn't) Only in a world that thinks rape is okay is it acceptable to speak so casually of it.
Not to mention, more than one THIRD of all women and one ninth of all men have been sexually abused, and this language is triggering. Even if you don't care about or believe in the effect of your words on the culture at large, consider the fact that if you are in public it is HIGHLY likely that someone within earshot has been a victim, and if you have more than two female friends it is extremely likely that one of them has been a victim. Sexually violent language can be triggering, and that means having that same emotion flood over you again. Not every victim will be triggered, true, but you have no way of knowing who will and who won't, as most people do not talk about being sexually abused, much less explain their triggers.
ETA: Rape has power, horrible destructive power, and to strip the word of that power would strip the act of its power in the minds of those who have never experienced it and leave them less likely to care, less likely to make change to stop rapes. The word rape needs to be a powerful word because the act of rape is a powerful act. Making the word less powerful would not make the act less powerful -- it would make the act have no appropriate word by which to call it. And if an act has no word to describe it, there is no way to open dialogue about it, which is the first step in working to stop it.
I refuse to be friends with someone who may use sexually violent language in a casual manner. To people I don't care about, I simply unfriend with no explanation when I see that, because it's never a nice conversation. If I pointed you to this post in response to you doing so, it means I care about you and want to give you the opportunity to reconsider your use of the word. I want to allow you to choose between losing the use of word in that way or losing me, as this is a firm boundary for me.