Denitsts, really, except maybe for a really bad dentist, it's not traumatic. Also if you actually at least take care of your teeth a little it shouldn't be painful, except again if it's a bad dentist. And although it's not my favorite thing to do I don't hate it, so not everyone hates it, the way you put it, you could argue that anything that isn't done for enjoyment, or cause joy, should be hated, say washing the dishes, if you don't enjoy it for some reason, is a chore, but i doubt most people would say they hated it, except maybe as a casual exaggeration.
Also the circumstances of rape and killing are rather different, killing is an act that can happen under many different circumstances, from accidental manslaughter to assassination and genocide, while rape has a rather narrow set of circumstances in comparison, yes the story around it may vary, but the broad central dynamic remains, there is one or more victims and one or more aggressors, like there is no such thing as accidental rape, it might happen when the aggressor isn't in their right mind, but it's still a conscious, more or less, decision. For example, in a fight, not to the death, one fighter may kill the other due to an unlucky blow or lack of experience whilst using some potentially lethal move. But the act of rape, if uninterrupted, lasts usually until the aggressor is satisfied, which is longer the few seconds that it required that fighter to accidentally kill his opponent.