He was treating them as people who matter. And, secondly, Jesus was doubtless being himself with them, which would mean he was communicating to them what mattered to him. To reduce all this down to Jesus making evangelistic forays into the pub to call wicked people to repent distorts the evidence, though one could head in that direction on a onesided reading of Luke's glosses to the first two parables. Few, especially among scribes and Pharisees, would have objected to Jesus turning up at such gatherings to announce repentance. The problem was that Jesus put the loving first, rather than keeping it till after repentance.
People matter most.
It was in that sense unconditional love, but this should not be seen as love which does not care about how people are and what they are doing to themselves. So Jesus talks about a typical human situation and tweaks it with some elements which make it spin. Father, not knowing anything but that the son is coming, abandons cultural norms of fatherly dignity, runs to embrace son. So meals were a place of controversy for Jesus. But we remember he also made much of them in his own movement and they feature regularly as an image in his teaching.