Marxist-Leninism by its very nature will attempt to betray all other non-authoritarian friendly factions at some point, as the ideology at its core calls for centralized control under a 'vanguard', which inherently attracts people seeking dictatorial power.

The Spanish Marxist-leninist faction not only betrayed the Anarchists, but also an anti-stalinist Marxist faction, the POUM, as allowing them to remain would've made their consolidation of power more difficult. Instead, they called the POUM 'secret fascists' that were collaborating with the enemy, and laid the same claim on the Anarchists, to justify the purge.