Am I my brother's keeper? (Gen 4:9)

In the reading at Mass today, from Leviticus, we are told,

"You must openly tell him, your neighbour, of his offence; this way you will not take a sin upon yourself." (Lv 19:17)

If, therefore, we know someone who willingly missed Mass the week before, should we tell them not to receive communion until they have gone to confession?
This is hard, because often the person doesn't want to know. It could make people angry. Yet fraternal correction is taught, as Jesus Himself says,

"If your brother does something wrong, go and have it out with him alone, between your two selves. If he listens to you, you have won back your brother." (Mt 18:15)

 According to the Catholic Encyclopedia, we only take the sin of another upon ourselves when we neglect to admonish the other under the following conditions:

• the delinquency to be corrected or prevented is a grievous one;
• there is no good reason to believe that the sinner will adequately provide for himself;
• there is a well-founded expectation that the admonition will be heeded;
• there is no one else just as well fitted for this work of Christian charity and likely to undertake it;
• there is no special trouble or disadvantage accruing to the reformer as a result of his zeal.

 Admonishing the sinner is a spiritual work of mercy which, alongside the corporal works of mercy, are the ways in which we bring Christ to others and recognise Christ in others. Those who fail in these forms of almsgiving receive the judgement of Christ, as today's Gospel tells us:

"He will answer them, ‘Amen, I say to you,
what you did not do for one of these least ones,
you did not do for me.’
And these will go off to eternal punishment,
but the righteous to eternal life.” " (Mt 25:45-46)

Christ in Majesty, in Angers Cathedral