It is a sin to believe evil of others, but it is seldom a mistake.

Related:

• Evil is that which one believes of others. It is a sin to believe evil of others,
  but it is seldom a mistake. -- H.L....
• I believe that all government is evil, and that trying to improve it is largely a waste of time.
  H. L....
• The great artists of the world are never Puritans, and seldom even ordinarily respectable.
  H. L. Mencken, Prejudices, First...
• To be in love is merely to be in a state of perpetual anesthesia -
  to mistake an ordinary young woman for a goddess. ...
• The most costly of all follies is to believe passionately in the palpably not true.
  It is the chief occupation of mankind. -- H. L. Mencken...
• It is hard to believe that a man is telling the truth when you know that you would lie if you were in his place.
  H. L....
• H. L. Mencken suffers from the hallucination that he is H.
  L. Mencken -- there is no cure for a disease of that...