Shake the dust off of your feet against this heretic. Nothing good, edifying or Holy can come from further conversation with them.
The most disturbing passages in the NT involve those who insisted they were sinless. They were very proud of what they accomplished.
Luk 18:12 I fast twice a week; I give tithes of all that I get.'
Luk 18:13 But the tax collector, standing far off, would not even lift up his eyes to heaven, but beat his breast, saying, 'God, be merciful to me, a sinner!'
Luk 18:14 I tell you, this man went down to his house justified, rather than the other. For everyone who exalts himself will be humbled, but the one who humbles himself will be exalted."