Yup, I’ve read it. Of course, all his “friends” turned on him in hatred after his conversion away from the dark side.
Yes, the 'Marxist Shunning' and experienced by most who 'dare' to challenge Marxist 'group think'. Shunning another aspect of 'control' i.e. a passive but powerful control. David's parents, who, after a life-long support of communist Party; suffered a permanent shunning from their community because his Mother asked a 'challenging' question of Party Leader at meeting.
If remembering correctly; this happening, not long after Kruschev outed Stalin - so a great deal of upset in Party that was embedded in New York's communist enclave 'Sunnyside', where David grew up.
(Easy to see the parallels of 'ism's that are rooted in totalitarian/ism - including in particular and most importantly - radical Islamism, which explains the Left's political empathies. . .)