You can tell from the way he says that to both Ruth and Gene that he's convinced HIMSELF. And maybe it's partly true - he could be a con artist AND committed to "quality."
One of the cleverest things about it is how he lectures Columbo about his eating habits and his cigar smoking. The person investigating the murder he committed is the last person he should be lecturing about his health! But being Milo Janus, he can't help it.