No, I really don't think so. It is his own responsibility.

If anything, it probably would have been rash if not scandalous to try to stop him; certainly if you attempted during mass.  Because then you make a scene, then others are scandalized-- if not by the scene itself, by the fact that now they are "aware" of this man's sins, and are all scrambling to figure out how to react, and asking themselves the same questions that you're asking yourself; not to mention the undue stress and strife placed on the priest who would then need to respond to the situation-- but he can't deny the man holy communion unless the man is a public sinner, heretic, schismatic, or excommunicate.  But if he doesn't refuse Holy Communion to the man, then there is the possibility once again for scanda by the fact that an entire congregation is looking at this man and judging him to be unworthy of receiving Holy Communion, and expecting the priest to do something about it.

So no, you did the right thing, at least judging by the information available.

If you have very serious and well-grounded reasons for believing that this person was in the state of mortal sin then you should definitely encourage him to go to confession.  Maybe share your concerns with the priest, without identifying your friend.

Pray and fast for your friend. Let him know that you cannot continue any relationship with him if he persists in using dirty language or in attacking the Holy things of God: especially His Saints and the Blessed Virgin Mary.

I will certainly remember him in my prayers.

Lord Jesus Christ have mercy on him.

Oh Holy Mary, Help  of Christians, intercede to God for us that he may be saved.

In her revelations to Ven. Maria de Agreda, the Blessed Virgin devotes an instruction to the theme of not sitting in judgment of other people. It is in the chapter when she was pregnant with Jesus but before Joseph was aware of the miraculous cause of her pregnancy.
The Blessed Virgin said that even if someone appears to be in the state of mortal sin we are not to sit in judgment against that person.      

Judge the outside, Christ said, "You will know them by their fruits".  I agree, that if a priest knows a soul, he should refuse.  A priest has to answer to God.  When Christ gave the apostles the power to forgive, He stated what sins you forgive they are forgive and what sins....

The scripture to which you're appealing is generally understood by the commentators to refer to doctrines; i.e., you will know them by what they teach.

If a priest "knows" a soul he should not refuse.  If a person falls under some established legal category of those who have no right to Holy Communion, then he refuses.  And then he is obliged to refuse.  Otherwise he is obliged to provide Holy Communion.