Isn't sending him to his desired afterlife rather a favor than a crime?
1) Just because the inevitable destination is nice, they may not be chomping at the bit to go. After all, assuming that not every single religion says Suicide is BAD and you are PUNISHED for it, why aren't people killing themselves in droves just so they can go to a nice afterlife?
2) Just because the individual is getting to go, the people they leave behind are impacted. You kill a parent, their children grow up orphans. You kill a priest, the people he could have saved are now lost. You still Impact the World.
3) Their afterlife may very well be merit-based. Meaning, the longer they lived/the more "Works" they did in the name of their god, the better the afterlife is for them.