Saying that the Messenger (sallallaahu alayhi wasallam) erred in the ways and means of da'wah is a revilement because the ways and means of da'wah are tawqeefiyyah (only come from revelation) and da'wah is from ibaadah (worship), and imputing error to the Messenger (sallallaahu alayhi wasallam) in this arena is a revilement. This does not mean that the Prophets and Messengers cannot make mistakes, since Ahl al-Sunnah affirm that minor errors can arise from the Prophets and Messengers.
The issue is stating that the Messenger (sallallaahu alayhi wasallam) erred in ways of da'wah which are tawqeefiyyah. The matters which are tawqeefiyyah are those the Messenger cannot act upon unless he receives revelation regarding them first. Al-Hajuri explicitly states in his audio that (هذا من وسائل الدعوة التي أخطأ فيها الرسول صلى الله عليه وسلم), "This is from the ways of da'wah in which the Messenger (sallallaahu alayhi wasallam) erred." So when this is understood and when it is known from history that Ahl al-Sunnah have been fighting against the people of Hizbiyyah for decades regarding this issue that the ways and means of da'wah are tawqeefiyyah (restricted to evidence) and not ijtihaadiyyah (down to personal ijtihaad), then it is an error from al-Hajuri to utilize this example to say that the Prophet (sallallaahu alayhi wasallam) erred in the "means of da'wah." The issue is not about saying the Messenger can fall into minor mistakes - that is agreed upon by the majority of the Scholars, that the Prophets and Messengers can fall into minor mistakes not connected to the conveyance of the message and which they never repeat or persist upon.
The followers of al-Hajuri have put up lengthy defenses of al-Hajuri, quoting from the Scholars past and present, affirming the the Prophets and Messengers make minor errors and errors in ijtihaad and that they may be corrected by revelation, using this to exonerate al-Hajuri.
However that is not the actual issue here. The actual issue is that "the ways of da'wah" are tawqeefiyyah, i.e. can only come from revelation. So al-Hajuri's error is that in misreading this incident, he has reviled the Messenger (sallallaahu alayhi wasallam) by claiming he erred in a matter which is really tawqeefee. The correct understanding of this incident is that the Messenger (sallallaahu alayhi wasallam) would have been more correct in choosing the more befitting of the two situations, which is attending to the blind man than to those from the Quraysh, even though both are acceptable - and this has no connection to what we refer to as the ways and means of da'wah, as that is a separate matter. However, al-Hajuri brought three examples, all of which he entered into the "ways and means of da'wah" and these examples are a) the issue of the blind man (80:1-2), b) the issue of repelling some from his companions in order to receive certain noble people from the Quraish (hoping for their Islam) (6:52 and c) supplicating against certain people (3:128). So he used these three incidents to show the Messenger allegedly erred in the "ways and means of da'wah," saying, (هذا من وسائل الدعوة التي أخطأ فيها الرسول صلى الله عليه وسلم), "This is from the ways of da'wah in which the Messenger (sallallaahu alayhi wasallam) erred."
What is more correct is to say this is an ijtihaad the Messenger (sallallaahu alayhi wasallam) made in which he was corrected by revelation, and in this, there would have been no issue in reality against al-Hajuri. But that is not what we are actually dealing with. This also shows that all of these defences being put out to exonerate al-Hajuri from blame from saying (هذا من وسائل الدعوة التي أخطأ فيها الرسول صلى الله عليه وسلم), "This is from the ways of da'wah in which the Messenger (sallallaahu alayhi wasallam) erred," then they are out of place, because no one denies that the Prophets and Messengers can make mistakes and that they can be corrected for these mistakes by revelation.
And as for the bold statement that "we do not take the saying of anyone, even the Messenger, except with proof," this was made by one of the followers of al-Hajuri and affirmed by al-Hajuri, and this is a type of boldness and disrespect of the Messenger of Allaah (sallallaahu alayhi wasallam), because the saying of the Messenger (sallallaahu alayhi wasallam) is proof in and of itself. But you have to understand the mentality here, this is the type of tarbiyah given by al-Hajuri and his followers to students and they end up with a bold and courageous attitude towards the people of knowledge. Namely, that if the Prophet (sallallaahu alayhi wasallam) erred in matters of da'wah and the Companions made many grave mistakes as well, innovating into the deen of Allaah, then the field is open to the first degree for us (the Hawaajirah Haddaadiyyah) to speak of the Scholars, and not to remain silent against them and their errors. However, as has been illustrated, when you do not have the fiqh of the deen to understand what is an actual error and opposition and what is an acceptable ijtihaad, or an erroneous ijtihaad, and when you yourself make grave and serious errors in matters of belief and in the usool of the religion, then this - coupled with that false attitude towards the Messenger (sallallaahu alayhi wasallam), the Companions, the Salaf and the Scholars of Ahl al-Sunnah in general - this is recipe for disaster and this is what we are witnessing now and over the past few years from the Hawaajirah Haddaadiyyah in different parts of the world. There is no worth to any scholar or any place or location except al-Hajuri, the "Imaam of the Thaqalayn", the "star amongst stars" and there is no vanguard for Islam except Dammaaj and everyone and everything else is under the feet!