Suppose, for a minute or so, if the Communists (Red Block) had not betrayed the Anarchists (Black Block/White Block), and they stayed a semi-united front?
Would the movement be stronger?
Who would have more members?
Would Communism have spread more rapidly?
Would Communism have longer sticking power?
In OTL, Communists are back-stabbing anarchists, even the white block (peaceful) anarchists. After a couple of centuries of this, you can tell why the fractures are deep, and Communism receive barely lip service from Anarchists.
Add some more questions after you put your input.
Some examples known are the Spanish Civil War, the Russian Revolution and of course, today, with every anarchist on edge for any sign of Communist activity against Anarchists, is both humiliating and divisive.