1918:

"To announce that there must be no criticism of the president, or that we are to stand by the president right or wrong, is not only unpatriotic and servile, but is morally treasonable to the American public."

2004:

Two Bush opponents, taken out of the crowd in restraints by police, said they were told they couldn't be there because they were wearing shirts that said they opposed the president.

(Both via Looka.)