Death Sentence? Life Sentence?

I am an opponent of the death penalty.

Although I can imagine situations in which it would be, "the only possible way of effectively defending human lives against the unjust aggressor," I believe such situations are exceedingly rare, (if not quite "practically nonexistent" -- for instance, had Bin Laden been taken alive I think his presence in prison would have endangered his guards and their families, his captors and their families, and indeed everyone of, in or connected to this country, to an unacceptable degree.)

 Assuming that the guilty party's identity and responsibility have been fully determined, the traditional teaching of the Church does not exclude recourse to the death penalty, if this is the only possible way of effectively defending human lives against the unjust aggressor.
If, however, non-lethal means are sufficient to defend and protect people's safety from the aggressor, authority will limit itself to such means, as these are more in keeping with the concrete conditions of the common good and more in conformity to the dignity of the human person.
Today, in fact, as a consequence of the possibilities which the state has for effectively preventing crime, by rendering one who has committed an offense incapable of doing harm - without definitely taking away from him the possibility of redeeming himself - the cases in which the execution of the offender is an absolute necessity "are very rare, if not practically nonexistent."

But apparently Pope Francis said things that were a bit more striking than what was reported in the Vatican blog's entry on his address to the Penal Association.
All Christians and people of goodwill are called today to fight not only for the abolition of the death penalty be it legal or illegal.
I do not think that is strictly true, (unless he means "called" by him.)
The Church Herself, as demonstrated in the section of the CCC quoted above, does NOT call us to do so.
I believe one can make the prudential judgment that it is ethical and moral to have the extreme penalty authorized in the event of extreme cases.

He further said, that we are called to fight,

for the improvement of prison conditions in the respect of the human dignity of those who have been deprived of freedom.

Very good.
But he went on,

I link this to the death sentence. In the Penal Code of the Vatican, the sanction of life sentence is no more. A life sentence is a death sentence which is concealed.

I can think of no suggestion more calculated to win converts to the propriety of the death penalty than to tell societies with legitimate fears of real evil that giving a life sentence to those whose crimes, whose, yes, sins evoke that fear, cannot be assured of the permanent incarceration of such criminals for the protection of the rest of humanity..