It's thou shalt not _murder._
The King James of the famous, often great prose but iffy in _accuracy_ bible he sponsored was the son of Mary, Queen of Scots, and was under great threat in England, like the Gunpowder Plot (Guy Fawkes and company, a Catholic plot), the struggle between Protestants and Catholics was vicious in his day. From Wikipedia is this chilling note:
"He was strongly committed to a peace policy and tried to avoid involvement in religious wars, especially the Thirty Years' War that devastated much of Central Europe."
As in, many Germans think it was worse than the results of losing WWII, and I can totally see that. And his son King Charles I was executed, which then put Cromwell in power.
*Vengeance* is a dangerous path, and in a state with a functioning legal system is to be avoided, so you avoid things like blood feuds (see my previous postings on this). Killing lethal enemies before they kill you is another thing altogether, which I won't get into here.