Many years ago, I discovered that nothing was ever gained by getting into an argument with someone whose mind was made up, and who wasn't open to the facts. I've made it a point, therefore, not to answer such people.
Unfortunately, your neighbor sounds like he's probably like this. As an atheist, he's not only opposed to God, but he's also opposed to anyone who speaks for God or takes a stand for what the Bible teaches. Perhaps he once read about a preacher who went astray in some way; sadly, it does happen occasionally (just as it does in almost any other profession).
But to claim therefore that all preachers are crooks is, of course, illogical -- and not supported by the evidence. I suspect that if your neighbor looked at the churches in his community, he'd probably find many of them are helping feed the hungry or provide for the homeless in their community, often at great sacrifice. Paul urged his young pastor friend Timothy to "set an example for the believers in speech, in life, in love, in faith and in purity" (1 Timothy 4:12).
Pray for your neighbor; only God can change his heart and overcome his pride, so that he'll face honestly his need of God's grace and mercy. But pray too that God will help you to show -- both by your life and your words -- that only Jesus Christ can give lasting hope and meaning to our lives.