Problem. This passage is about a woman caught in adultery, not prostitution. The mob wants to stone her to death on the spot, never mind a trial. They are operating outside the law. Jesus' beautiful solution is to ask the one who is without sin to throw first. They are not so far gone that they deny their own sinfulness. When they slink away, Jesus tells the woman He will not condemn her, but ends with "sin no more." Few seem to want to quote that bit.
Jesus forgives our sins. (Thank You. Thank You. Thank You.) He can do that while maintaining justice because He took the punishment for sin on the cross. He expects us to quit the sins, not to go our merry way, pounding in a few more nails.
"Not many of you should presume to be teachers, my brothers, because you know that we who teach will be judged more strictly." (James 3:1) And Matthew 18:6, “If anyone causes one of these little ones—those who believe in me—to stumble, it would be better for them to have a large millstone hung around their neck and to be drowned in the depths of the sea."
Whether you believe the Bible or not, you have to see that John 8 has nothing to do with the legality of prostitution. When a "pastor" uses it to promote a sinful practice, to tell women that there's no sin in selling their bodies for sex (and apparently no blame for the customers either), he is certainly causing them to stumble. He will face judgment one day. The one Who truly is without sin, the one Who is the living Word, will teach him just how sharp is the Word of God.