Explanation: A common argument of Soviet apologists is that everything the Soviet Union did was, in some way, dictated by 'material conditions', and thus necessary for the development of Socialism(tm). Obviously, this line of argument is dubious to begin with, but beggars belief when applied towards the Soviet Union's instances of ethnic cleansing and genocide, which are either denied or so justified.
Anarcho-Communists tend to be more critical of... well, everything. The CNT-FAI was an anarchist trade union which was one of the major players in the Spanish Civil War. After offering amnesty to all criminals to begin with a clean slate, they implemented work/detention camps for criminals convicted by local tribunals and fascist PoWs. Since prison abolitionism is a common cause amongst modern anarchists, they're less willing to go to bat for 'Good Team' when it contradicts their basic moral code, even though the CNT-FAI is one of the most beloved examples of anarchist praxis in the 20th century.
