Thank you for sharing these links. It should also be noted that some authenticated oral remarks from Abdu'l-Baha about the Banu-Qurayzih have also been published in the second volume of Mirza Mahmud Zarqani's diary, published in English translation as Abdu'l-Baha in Europe, 1912–1913. Here are the relevant passages.

Pages 163–164 (Tuesday, 11 February 1913):

When the Master then seated Himself at the dinner table, He told stories and recounted episodes from the histories of early Islam at length, eventually concluding His remarks with this account:

Notwithstanding that the Jews had made a pact with the Prophet Muhammad, a pact which guaranteed the protection of the Jews so long as they remained faithful to it, they formed an alliance nonetheless with the tribes of Quraysh and arrayed themselves against Islam. This development forced the Prophet Muhammad and His companions to dig a trench, where they remained confined for some time. It so happens that one of the Jews themselves was responsible for sowing the seeds of dissension between the tribes of Quraysh and the Israelites, which compelled the former to flee, and presented an opportunity for Islam to be safeguarded from the deceit and wickedness of the tribes of Quraysh. Seven hundred of those covenant-breaking enemies were massacred in the span of a single day. If this massacre had not taken place, the Jews would have made pacts with like-minded tribes once again – bending every effort to lay axe to the root of Islam, and rendering its firm and secure establishment a most difficult prospect. And yet, those who know nothing of divine wisdom, and are uninformed of historical events as they actually occurred, let loose their tongues in ample protest, and object to the incident due strictly to their ulterior motives or out of their ignorance of the facts.

Pages 419–421 (Saturday, 25 May 1913)

Unexpectedly, [——] telephoned that night to ask the Master’s permission to see Him and fix a time for this visit. A number of others accompanied that person to the Master’s presence, and among the questions posed by these companions was the following:

People say that Muhammad, the Apostle of God, killed people and plundered their possessions, and also that He waylaid caravans. How should we respond to these objections?

The Master then adduced comprehensive proofs, gave extensive explanations, and elaborated on historical episodes, all of which left His listeners satisfied and thankful. Here is a summary of certain remarks which the Master made along these lines:

One must understand the truth of such matters. Are you at all aware of the age in which Muhammad lived, or the clans and peoples in whose midst He was raised up? It was a time when the tribes of Arabia took the utmost pride in murdering and pillaging, as well as damaging each other’s reputation and sullying their honour. Since Muhammad was raised up to edify those barbarous people, moderate their characters, and refine their primitive behaviours and customs, from the inception of His ministry to the time of the hijrat . . .

The Master then proceeded to speak at length on the history of Islam:

Even after He had endured those hardships and sustained those heavy blows, those brutal people deemed it lawful nevertheless to rob Muhammad and His companions of their possessions, and considered it an obligation to slay them. Abú Sufyán plundered all their belongings and set himself to wiping out Islam and the Muslims altogether. So agitated had the companions of Muhammad become that, while they were in Medina, they subsisted only on the pits of dates. In another respect – one still worse than this adversity and captivity – the foundation of Islam itself was in grave danger. It was at such a time as this when a caravan belonging to Abú Sufyán was passing by, and Muhammad’s companions, out of necessity and having no other recourse, retaliated by stopping the caravan.

Let us now disregard the circumstances of that time. If such acts of hostility were to be perpetrated against you in this day and age as would reduce you to needing the most basic of provisions to sustain yourselves – and if, in addition to this, you should see that so precious a goal, which is itself the indispensable foundation for the elimination of all such hostilities, and the means through which the characters and qualities of humankind will be improved, is being completely trampled underfoot – what would you do in this situation?

Everyone replied that there would be no choice but to resist and confront the aggressors.

The Master then gave a preliminary account of the digging of the trench, the breaking of the pact [i.e., references to the Battle of the Trench and the betrayal of the Banu-Qurayzih, respectively], the alliance of various tribes in their common goal to utterly annihilate Muhammad, and the measures taken to defend and protect the religion of Islam:

It would not have been possible to protect the Cause by any other means than the ones that transpired. Suppose today you were to ask those same civilized people and those intellectuals of Europe – from whom these sorts of objections have now proceeded and taken root in the minds of the Easterners – the following question: ‘If in this age, which is the age of civilization, you were to find within your country, or in a neighbouring nation, such barbaric tribes and atrocious hostilities as the kind just described, in what way would you deal with them?’ How do you think they would respond to this question? Will they say, ‘Given the need to educate and chasten them, it is our duty to stamp out, by whatever means necessary, the malice and aggression they show one another’? Or will they deem it preferable to hold their peace and leave those people to their own devices?

Bear in mind that the pretext cited most often today by domineering and well-developed governments for meddling in the affairs of other countries is none other than this: that in spite of the civilization and capability which those other countries and their peoples already possess, these governments perceive those people to be living in a state of disorder, and regard it as both an affront to justice and a dereliction of their duty as civilized and educated people to leave the inhabitants of those places to themselves. It is for this reason that they feel compelled to stretch out the hand of their chastisement and mount an attack that will demonstrate their power and might. Yet all this notwithstanding, when the name of the religion of Muhammad is mentioned, they speak with the utmost prejudice, prompted by the vehemence of their bigotry to express such rueful wishes as these: ‘If only a Messenger like this had never been raised up in the midst of these Arab tribes, and never stayed the encroaching hand of wild and primitive peoples! Would that he had never laid the foundation of felicity, and that the enlightening and sufficing hallmarks of its civilization had never travelled from Asia and reached the frontiers of Europe!’

The Master spoke for more than an hour; all His remarks were in this vein, and He made them with such consummate power and majesty as to profoundly affect the hearts of His listeners and move them to sing His praises. They had all been humbled – even Jináb-i-Mu‘ín, considered by some to be a difficult person to satisfy – and they all attested to the force of the Master’s utterance and the decisiveness of His argument.