Tax-collectors worked for the hated Romans so they were universally despised. 'Sinners,' were a demographic in Jewish society who were looked down on by the religious professionals. The Pharisees could think of no more scathing remark to direct at Jesus, than to observe how he enjoyed the company of outsiders and riff-raff. They did not know that their criticism was a preaching of the Gospel. God does indeed welcome those who are unwelcomed by everyone else.
I'm busy working on my blog posts. Watch this space!