Harry Truman actually said...
The standard for the refusal of employment or the removal from employment in an executive department or agency on grounds relating to loyalty shall be that, on all the evidence, reasonable grounds exist for belief that the person involved is disloyal to the Government of the United States.
Context
Executive Order 9835—Prescribing Procedures for the Administration of an Employees Loyalty Program in the Executive Branch...
03/20/1947