Mortalium (animos??), you are trying to do a good work, a spiritual work
of mercy, instructing the ignorant. Ironically, he is the "professor" and you
are the "student." The principle of ABL comes to mind, "The superiors form
the subjects; the subjects do not form the superiors."
Therefore, the more you persist in this good work, the more danger there
is to your own faith, merely by dint of his position of authority, which he
will no doubt attempt to use to influence your thinking, even if it is in very
small ways at first.
The advice of TKGS above, and on the first page are very good. You are
well advised to read them several times. Especially Pascendi: you not
only must merely READ it, you must STUDY it. It takes more than one
read. There is an excellent book, called A CATECHISM OF MODERNISM,
by Fr. Lemius, available at TAN Books. It is a tremendous teaching aid
for anyone who wants to A) understand Pascendi very well, B) use the
principles and treasury of Pascendi to help them identify what Modernism
is in our daily lives, C) take our own comprehension of this important
reality and be able to help someone else to see the reality of Modernism
in their own life and subjective concept of their "faith."
One thing I took out of this great book is, that Modernism is a disease of
the spirit to which we are all subject due to the fact that we live in the
age that we do. But since we are IN IT, we cannot SEE IT. It seems
"normal" to us "because everyone's doing it." But still, it is a spiritual
malady, and one of its symptoms is, you do not know you are infected.
In other words, properly understood, not finding yourself suspect of any
"infection" with this spiritual malady is no assurance that you are not
infected, because your own abiding ignorance of your infection is one
of the symptoms of the disease!
You can reformulate that doctrine and keep it at hand when you speak to
this guy, and just drop in various permutations of the principle at different
moments, in the event that at some point perhaps it will click in him. You
cannot get ANGRY or PASSIONATE or DISRESPECTFUL at any time,
because then he'll write you off as a "Bible thumper" or a "wacko."
But I would be careful not to give him too much of your time. Come
well prepared and just give him a few minutes.. for as Fr. Pfeiffer says
so compellingly, when it comes to Modernists in positions of power, it
is useless to argue with them. It is like arguing with a woman.. you will
never win. Keep it simple, keep it firm, drop your message, and leave.
The example I'm thinking about is at about minute 10 of his Laetare
Sunday sermon (over an hour duration!) and is quipped on the back
pages of the most recent The Recusant (Issue 6), page 30 actually.
If you don't have it, I can copy it here for you. It's called "Fr. Joseph
Pfeiffer on Bishop Fellay and the Preamble" (he means "his Response to
the Preamble," or "his Doctrinal Declaration of April 15th, 2012").