Anti-Communism vs. Capitalism
(EN: Pause here to consider that this book was published in the 1950s during the time of McCarthyism. During this period, the fear of communism gave rise to a backlash that violated many of the core principles of capitalism and democracy for the sake of protecting them.)
The author is concerned about the "anticommunist" movement that had taken hold in western government. It opposed communism on the grounds that it is a totalitarian society that negates individual freedom - but in doing so it proposed a totalitarian society that would negate individual freedom.
It is not that they wish to protect America from domination and slavery, only to protect America against foreign domination and instead impose a dominion of their own. Their ideals and their methods clearly demonstrate that they are not at all objecting to the people being controlled, only to the identity of those who will be in control.
While it is sensible to resist the intrusion of totalitarianism into America, it is not sensible to do so at the cost of the liberty of the people - this is like burning down one's own house to protect it from an arsonist. It should be sufficient to protect the people from any who wish to interfere in their liberty, be these aggressors foreign or domestic.
While communism seems a serious threat in the present day, it is unlikely to have any longevity. The notion of a centrally controlled economy is incompatible with success and it will, like all "socialist experiments" meet with an inevitable failure. It does not require an aggressive defense, just a mild resistance and the patience to wait until it fails of its own accord.