Coffee was once considered to be a gateway drug by some doctors in the 19th century. To quote one T.D. Crothers, M.D. -

"Often coffee drinkers, finding the drug to be unpleasant, turn to other narcotics, of which opium and alcohol are the most common."

Coffee was also oppressed by Muslims in some places - people used it to stay awake during long prayer sessions, which was considered improper.