Anyone who has read up on the second Red Scare knows that it was very real. That the commies had infiltrated the government especially the State Department, Hollywood and academia. They got knocked back a little but came back stronger than ever in the 60s.
Maybe he thought no one would check on his remarks and why he made them:
He likened the current climate of “fear, suspicions and prejudice” against Muslim immigrants to the Red scare and McCarthyism his grandfather, Charles S. Johnson, lived under in the 1940s and 1950s.
In 1949, Johnson, a sociologist and president of predominantly black Fisk University, was dragged before the House Un-American Activities Committee and “asked to deny if he is or ever has been a member of the Communist Party.”
The panel had good cause to investigate. Communists hadn’t just infiltrated Fisk as professors, but Johnson had readily hired them, including Giovanni “Ross” Lomanitz, a known communist operative.
Even after Lomanitz’s communist loyalties were exposed, Johnson spoke out on his behalf. Johnson then hired and defended yet another communist, math professor Lee Lorch. Johnson initially refused to fire him, but relented under withering criticism.
There was also the issue of Johnson’s own membership in communist fronts such as the National Sharecroppers Fund.
People did not fully understand why this was happening (in some cases it was because the Red Army was present to assist the local Communists), but they knew they didn't want the same thing to happen in the USA. Even the Truman administration made some efforts to weed out Communists from the federal government. The Alger Hiss case attracted a lot of publicity.
Poor Jeh's grandfather gets called to testify because he is hiring Communists at Fisk University. The horror!