I Find This Instructive

From the Online Museum on Communism:

Nominally, the FF government represented a broad coalition that included, in addition to communists, agrarians, social-democrats and independents. In practice, however, the communists, buoyed by the logistical and political support of the Soviet Army, immediately took complete control over the state’s coercive mechanisms and began to terrorize their political rivals. Some of BCP’s leaders –like Georgi Dimitrov and Vulko Chervenkov, were in Moscow, while others like Traicho Kostov and Anton Yugov were in Sofia. But all communicated to their followers a simple and compelling message: the time had come to get rid of the “bourgeois scum.” By the end of November 1944 approximately 5,000 Bulgarians were killed, including teachers, priests, civil servants, writers, journalists and civic leaders.

Why are the first targets of a communist take-over usually "Teachers, priests, civil servamts, writers, journalists and civic leaders"?

Aren't these the backbone of the progressives in the United States?