“If we understand the mechanism and motives of the group mind, is it not possible to control and regiment the masses according to our will without their knowing about it? The recent practice of propaganda has proved that it is possible, at least up to a certain point and within certain limits. ”

The motives and mechanism of the group mind are soon molested by the political spirit of corruption and hatred. Truth and accurate reasoning are the first to fall by the wayside. Pearls of wisdom concerning Brakah liberty and freedom are soon trampled underfoot. 

The answer is Yes! It is possible "to control and regiment the masses according to our will without their knowing about it."  It has never been more apparent in the mass media and social media.  The propagandist does not need 100% belief by all; to convince a small but loud minority is enough to sway the masses, if only to disrupt and attack the opposition.  Propaganda is a form of war upon the individual, to bring him/her into line, to control the 'narrative' and adopt it as one's own.

Hmmm, the group mind — a collectivist mind set. Starting with an individual that has been sufficiently brain washed with an inability to perceive inalienable rights and liberty outside the hive does offer a mechanism to control the masses without their knowing about it. The recent practice of puppet masters’ propaganda concerning this last election proved - fraud, lies and all forms of criminality can be successfully implemented. The Declaration of Independence (“all experience has shown, that mankind are more disposed to suffer, while evils are sufferable, than to right themselves by abolishing the forms to which they are accustomed.”) supports the meme’s concept of “up to a certain point and within limits.”