Where you go wrong is the difference between theory and excuse. U.S. installed fascists because they were usefull to suppress dissent abroad, the same way corporations and Fox news now support dictators in Hungary and Turkey abroad and Trump here to suppress dissent. The slippery slope of Social Democracy to Communism was just the useful excuse. It didn't have to be remotely true to be useful in the same way Obama's Republican sourced Healthcare plan didn't really make him a Marxist, it didn't stop Fox news from calling him that constantly and their base from believing it. Pretending an excuse is a reason keeps you fighting with shadows.