Because he's killing in the name of "god". That pretty much makes him no different than anyone else killing in the name of god.
Governor Hutchinson says he is confident that the drugs will work as expected, and that he is satisfied the prison staff can handle the executions, six of which are happening over only three days.[..]
"I have a responsibility to the voters, I have a responsibility to my oath of office, but I also have responsibility to a higher power, God and eternity, and I understand that," he said.
"I feel comfortable in my understanding of my responsibilities both in terms of faith and scripture and in terms of as governor." (BBC)
Yes he's "comfortable" killing people. Because he's "comfortable" that god is totally behind this and the bible says so.
About the only thing I'm "comfortable" with is living many, many states away from a religious zealot who justifies killing by the application of myths rather than rule of law.
You're pretty fucked up there Asa, and I'm pretty comfortable that other people feel the same way too...