There are some scoundrels, whose record of genocide, treason, crimes against humanity,  as well as the ongoing danger they present, who require a capital response.  Davis was one of the perpetrators.  He was allowed to survive and be regarded as that quaint leader of the rebel cause, as opposed to the man who led a rogue slave state that caused the death of many Americans.  How the south would have looked different had Lincoln and Garfield survived.  Arguably, there would have been no jim crow.

He would have been in league with al baghdadi, al zawahiri, mengitsu,  khalid sheikh mohammed, kim jong-un, and many of the leaders of the communist party of China who continue to survive their crimes. 

So, yes, I advocate capital punishment in the context of the crime committed.