Someone asked me (at that time) where I got that, and I don't think I really answered him, but today our pastor preached on the text that I thought was relevant.
Usually, when people say that Jesus ate and partied with sinners, it's based loosely around the passage where the Pharisees grumble against Jesus, saying that Jesus ate and drank with sinners. A quick look at that passage supports my view -
15:1 Now the tax collectors and sinners were all drawing near to hear him. 2 And the Pharisees and the scribes grumbled, saying, “This man receives sinners and eats with them.”
3 So he told them this parable: 4 “What man of you, having a hundred sheep, if he has lost one of them, does not leave the ninety-nine in the open country, and go after the one that is lost, until he finds it? 5 And when he has found it, he lays it on his shoulders, rejoicing. 6 And when he comes home, he calls together his friends and his neighbors, saying to them, ‘Rejoice with me, for I have found my sheep that was lost.’ 7 Just so, I tell you, there will be more joy in heaven over one sinner who repents than over ninety-nine righteous persons who need no repentance.
Context context: What prompts the Pharisees to grumble? The fact that these tax collectors and sinners were drawing near to hear him. Not that Jesus was going out of his way to watch immoral people, but that they were coming to Him.
And the parable that Christ tells to rebuke the Pharisees ends with the line that "there will be more joy in heaven over one sinner who repents than over ninety-nine righteous persons who need no repentance." The emphasis is not just upon the fact that they were sinners, but that they were repentant sinners.So that parable is directed by Christ against the Pharisees because they were accusing him of eating with sinners, but Christ is replying, "no, there is great joy in eating with sinners, just like there is joy in finding a lost son, because he is found."
While there may be other passages that disagree with the assessment that Christ only ate with repentant sinners (or those who had come to listen), this one passage certainly support that those there were repentant.