Isn't there something else in the Bible about 'hereditary guilt'? Something about guilt falling on someone's descendants for seven generations, yea, even unto seven times seven?

Sorry to be so vague, I am no Biblical scholar!

Isn't there a difference between "his blood be on our head" meaning "we are responsible for our guest" an ancient tradition (see Kadare Broken April for instance) and the meaning "kill him if you want, we will take the responsibility" ?

Perhaps Matthew 27:25 is also part of the ancient rules of the blood feud: 2Samuel 1:16 has a man of the same clan as Saul saying "Yahweh has brought upon you the blood of the House of Saul". When David has a man killed in Samuel2 1:16, he says "your blood be upon your own head" because the man has condemned himself out of his own mouth. The tribal context highlights the difference between such notions and the message of the passion of Christ, as made clear by the Archbishop.

Sorry, 1st reference is 2Samuel 16:8

As you point out correctly, the expression has to do with assuming responsibility, and is not a blood curse or anything of that sort. [1] Thus, in Joshua they are assuming responsibility for what happens, and in Matthew they are likewise assuming responsibility for the decision they take, i.e., to free Barabbas and have Jesus crucified.

[1] Although the expression probably originates in a time when it would have had a concrete meaning, and not only a metaphorical one.

The only difference between the two is that in Joshua, the assumption of responsibility is in hypothetical form: if something bad happens to him on the street ... or in the house ... because nothing has happened yet, and potentialities are listed, just as in a contract. Whereas in Matthew there are no potentialities but rather a known outcome and responsibility is assumed for that outcome (i.e., Jesus crucified).

Exactly. My point was that we have here both the hospitality-protection element and the tit-for-tat element of such relationships. It seems peculiar that for so many generations Christians, of all people, have been pursuing a kind of Sicilian vendetta on the basis of what was said. Even in normal blood-feuds there is some sort of statute of limitations.

Just like it wasn't the Jews in general who killed Jesus, but rather some Jews of Jerusalem with Roman involvement, it was not the Christians who persecuted Jews, but rather some Christians. Thus, we must not generalize to either all Jews or to all Christians

And, if we are to be objective, we will also acknowledge the crimes of Jews against Gentiles and Christians throughout the ages, and not only those of Christians against Jews.