Communists' rhymes with:
noncommunists, noncommunists, noncommunists, noncommunists, noncommunists, abortionists, agonists, balloonists, botanists, cartoonists, colonists, constitutionists, extortionists, hygienists, impressionists, internists, interventionists, isolationists, machinists, machinists', misogynists, noncommunists, nutritionists, opportunists, peronists, preservationists, protectionists, receptionists, rejectionists, reservationists, revisionists, revolutionists, secessionists, segregationists, shamanists, stalinists, unionists, zionists
Communists' sounds like:
chemists, coincides, comcast's, communicates, communist's, communists, comsat's, comstock, concedes, conestoga, conjugates, connaught's, connects, conquest's, conquests, consists, constitutes