He who holds the ladder is as bad as the thief.

Related:

• He who steals once is always a thief.
  Spanish...
• He who borrows sells his freedom.
  German...
• There's no thief like a bad book. --
  Italian...
• It is a beggar's pride that he is not a thief.
  Japanese...
• He who would rule must hear and be deaf, see and be blind.
  German...
• He that finds fault wants to buy.
  German...
• Who is not ashamed doubles his sins.
  German...
• It is not the thief who is hanged, but one who was caught stealing.
  Czech...
• There is no bad beer: some kinds are better than others.
  German...