I think there are generally good and bad within every category of beliefs and non beliefs.
For ones who would do as you say. The good ones were firm believers in a religion, and when they discovered it wasn't true, it was so devastating they lost faith in everything, if they looked at every religion they found untruth in every one. So they see believers as setting themselves up for hurt and get frustrated then may ridicule. If there is a chance just the entire world was blind, then truth comes out, and it makes sense, and answers controversies, they may believe again, but they would be very cautious this time and check everything. They are right completely free as well but they are good people, they still wouldn't steal, etc, they have morals even if they think this is the only life. If they do what is considered sin, it's based off of if it's hurting anybody else or not.
Then the bad kind, these ones do not have morals, and I'm not talking about anything that might be considered sin, I mean they will be unethical, thieves, pursue married people. They do not follow love and treat neighbor as you want to be treated. They hope and would resist very hard if proof started to come out about there being a real God. They would ridicule and really hope that when they die, if they got away with murder, they truly did.