We know Jesus' reply. But the Pharisee's question seems quite reasonable. They didn't have the whole story, of course, but it isn't crazy to question the company you keep. I can think of three ways they might be viewing this.
- Hanging out with unrepentant sinners drains away the power of shaming to bring home to them the gravity of their offenses. If their consciences are already seared by lives of sin, what other way do you have to get through to them except social sanction? We can easily see what happens when you lose those social sanctions.
- Hanging out with unrepentant sinners sends a confused message to third parties, especially children. Is their sin really sin or not--do you approve of it? If it's OK for him to hang out with bad companions, why can't I?
- Hanging out with unrepentant or only-just-starting-to-repent sinners immerses you in their attitudes. That will effect you. You expose yourself to temptation, and you'd better not be too proud to admit you can be tempted. Bad companions ruin good morals.
OK, Jesus is the healer, you won't successfully tempt Him to sin, and the Pharisees were making assumptions about the whether all the other guests were repentant or not (probably not without some warrant). In any event, Jesus is a special case.
Paul's pastoral rules suggest that the problem with bad companions remains for Christians. How do we reconcile the differences between the Pharisees' rules and Jesus'?
Two things strike me; one more obvious. In the stories of the sheep and the coin, the lost was something that belonged. The parable of the prodigal is about a member of the family. These tax collectors and sinners aren't supposed to be "other", they're supposed to be part of us.
The other is that Jesus' life was evidently such that no claim of sin would stick. Our lives should be too, so that we could sit down with the greedy rich and there be no suspicion that we're looking to benefit or think it a good alternative life style. I have a hint or two about how to do this, but it looks uncomfortable. Mea culpa.