As my friend TheoJunkie points out, (link), vengeance belongs to our God. That's why, even though we may view the pope as a leading enemy of the gospel, nevertheless we do not threaten his life, or encourage others to do so.
There is, of course, no more precarious state than to be an open enemy of the gospel of salvation by grace alone through faith alone in Christ alone.. The Bible states:
6But whoso shall offend one of these little ones which believe in me, it were better for him that a millstone were hanged about his neck, and that he were drowned in the depth of the sea. 7Woe unto the world because of offences! for it must needs be that offences come; but woe to that man by whom the offence cometh!
Mark 9:42 And whosoever shall offend one of these little ones that believe in me, it is better for him that a millstone were hanged about his neck, and he were cast into the sea.
1 Then said he unto the disciples, It is impossible but that offences will come: but woe unto him, through whom they come! 2It were better for him that a millstone were hanged about his neck, and he cast into the sea, than that he should offend one of these little ones.