I'm an ex-Christian, FWIW.
For me, "judge not", means that I did not use my faith to harm others. In other words, I believed that a certain lifestyle was preferable, but it was not right for me or anyone else to condemn people who were immodest, etc.
An example of who I would judge would be a family member who does not adhere to the rules of her faith (she;s Catholic, and doesn't go to church or confession EVER), yet uses her faith as a weapon to condemn others. I would consider that the most evil of all.