For various reasons, we are prone to read episodes and statements in the Scriptures--and especially those by Our Lord--assuming a tone of voice that is too often ours.
For example, in St John 13.27, "Jesus said to him, 'What you do, do quickly.'" Quite apart from whether Jesus is speaking to Judas or Satan-in-Judas, one needs to ponder what tone of voice Our Lord uses when He says what He says. Is He being snide and sarcastic? Is He challenging Judas, and telling him to get the sin over with?
That's how we tend to hear these words--especially if they are spoken rather than chanted. For the wonderful thing about chanting the Gospel is that our (conscious or subconcious) interpretive inflections are left behind. But that's another topic...
To assume that Our Lord is speaking like we do is to assume that He's letting His passions get the best of Him--that in His human nature, He's prone to get snappy and irritable.
If we acknowledge, however, that the Son of God became as we are, except without sin; and if we confess that, above all else, the Lord is merciful, then perhaps there's another way to read St John 13.27. Perhaps Jesus is not laying down the gauntlet or issuing an ultimatum--to Judas or Satan-in-Judas. Perhaps Jesus is urging Judas to do quickly what Our Lord has, for three years, taught him to do, and which Judas knows full well; namely, to repent by turning aside from his betraying plot.
To my way of thinking, this "tone of voice" seems most appropriate to Our Lord. Which means that He's not showing Judas the door; rather, He's pleading with him to reconsider and to "come home."