The footnote to the last sentence (#68) refers to Pope John Paul II's encyclical, 'Evangelium vitae' #56. 

Pope John Paul personally amended the Catechism to leave almost no wiggle room for capital punishment, and no wiggle room at all for a country like ours.  I'm the last person to deny that a Catholic has a right to dissent from Catholic teaching, and I certainly respect the right of Catholics to dissent from this teaching (though intellectual honesty ought to compel them to acknowledge that that's what they're doing.)

Kaine's moral problem was not that he dissents from the teaching, but precisely that he accepts and agrees with it.  I thought he did an excellent job of explaining how he wrestled with that problem and how he resolved it.