Shirley Temple wasn't called because they thought that she was a communist, nor was she called in the 1950’s. She was called in 1938 at the age of ten. Likely a move by the Congressmen to publicize the extent to which communist schemes were reaching. A dog and pony show perhaps, but that's about it.
By Soviet records they had very real success using agents and useful idiots, especially writers, to sway American society. The Hollywood 10 were charged with contempt for refusing to answer any questions after being subpoenaed. They specifically tried to put on a show, which their handlers (go figure) had instructed them to do.
The infamous “blacklist” was the result of public outrage and boycotts, not government mandate.