I wouldn't say that I approve, but when I think about it, if they hadn't raped someone, they probably wouldn't have ended up in jail with murderers in the first place.
I don't see how anyone can approve of this. To say that you do is to support a mandatory death sentence for sex offenders. What ever happened to rehabilitation?
Also, in case you're suggesting that the rapist's killers were in prison for murder, their reason for being in prison isn't mentioned.
I didn't assume they were in prison for murder. The fact that they murdered this guy makes them murderers.