The original letter may be found here, but here is a quick NLM translation of the most relevant paragraphs:
Letter to the Motu Proprio "Summorum Pontificum," Pope Benedict XVI
On the Celebration of Holy Mass
Dear Priests and Deacons,
It is with much bitterness of spirit that I have found that many of you have not taken up or made a right attitude of mind and heart toward the possibility given to the faithful by the motu proprio "Summorum Pontificum" of Pope Benedict XVI, of the celebration of Holy Mass "in the extraordinary form" according to the Missal of Blessed John XXIII, promulgated in 1962.
In the "Three days of the Clergy" of September 2007, I indicated with strength and clarity what is the value and the true meaning of the Motu Proprio, how we should interpret it and how we should accept it, with a mind that is open to the magisterial content of the document and with a ready willingness of a convinced obedience. The position taken by the Bishop was not missing its calm authority, strengthened by his full concordance with a solemn act of the Supreme Pontiff. The position of the Bishop was founded by reason of his theological argument on the nature of the Divine Liturgy, the immutability of the substance in its supernatural contents, and was also based on surveys of the practical, concrete, good sense of the Church.
The adverse reactions to the motu proprio and the theological and practical guidance of the bishop are almost always dictated by emotional and superficial theological reasoning, i.e. a rather poor and shortsighted "theological" vision, that is not part of and which does not reach the true nature of the things which concern the Faith and the work the Church's sacramental life, that is not fed by the perennial Tradition of the Church, which looks at rather marginal aspects or at least incomplete issues. Not without reason, had I, in "Three Days" cited above, prefaced with the operational guidelines and principles to guide action a doctrinal exposition on the "Unchanging Nature of the Liturgy".
I understand that in some areas, on the part of several priests and pastors, there was also the manifestation almost of ridicule toward faithful who have asked to make use of the option, and indeed of the right, for the celebration of Holy Mass in the Extraordinary Form; there is also an expression of contempt and almost of hostility toward Brother Priests who are well prepared to understand and respond to the requests of the faithful...
I ask that you put away every attitude not in conformity with ecclesial communion, the discipline of the Church and the convinced obedience due to important acts of the magisterium or government.
I am convinced that my call will be accepted in a spirit of filial respect and obedience.
The letter carries with it all my desire that it might help to reawaken and a strengthen our ecclesial communion and of our common desire to fulfill our ministry with a renewed fidelity to Christ and his Church.
Finally, I would ask you for much prayer for me and for my apostolic ministry, and I cordially bless you all.
Albenga, 1 January 2012, Solemnity of the Mother of God
Monsignor Mario Oliveri, Bishop
Now one might wonder why we would publish this letter, a letter directed by one bishop to the clergy of his particular diocese. The answer is rather two fold.
First, it is encouraging to see a bishop who is taking the usus antiquior seriously both liturgically and pastorally -- and I include within this latter category those clergy who also are attached to or interested in this form of the Roman liturgy.
Second, while this letter details an apparent situation, a climate, within the particular diocese of Albenga-Imperia, we know only too well that this same climate can also be found in most dioceses of the Latin rite. For that reason too, this letter and the words of this bishop surely speaks to a broader situation as well.