I'm sorry to contradict you, but this is completely wrong:
No, it isn't wrong at all.
There is no law in the world that will protect you from slander if you explicitly allow for the right to modify a work. You cannot sue a person for using a free software program in a manner that you consider bad since you explicitly gave this right. Same applies if you give the explict right to modify a text in anyway or form.
Copyright law (and licenses) are concerned with copying. They don't make void other laws. Who sells knives doesn't limit your use, but cutting throats is illegal nonetheless.
Comparing murder to modification of a text is a bit extreme specially when they have nothing in common.
The license you license software under, e.g. GPL, explicitly allows modification of the work. You cannot, ever, claim that it is wrong for a person to use the program in a manner that you find ethically wrong (porting it to a non-free platform for example). The same applies to a work where you give _explicit_ permission to modify the text.
You are confusing a already written work, and a work that doesn't yet exist where one invents something from scratch. The later is infact protected by libel, slander, and other such laws. The former is not.
Cheers.