The poachers aren't killed for their hunting crime, they are dangerous murderers. Here's 2 links:

https://www.iucn.org/content/rising-murder-toll-park-rangers...

http://www.poachingfacts.com/poaching-statistics/

I also advocate that these rangers should be allowed to kill poachers rather than just be killed by them. I think you're wrong and didn't read information regarding the topic. I reject your virtue signalling as appropriate.