Eh. Except many rapists are people known to their victim, who may not want either a) to kill the rapist themself, or b) to feel like, if they didn't kill the rapist then they must not have been saying 'no' loud enough, or c) to see someone else kill the rapist in some kind of revenge.

It's not homicide laws that need to be fixed, it's the way the justice system deals with rape.