Markov is referring to the show trial of Traicho Kostov, a Bulgarian politician who fell out of favour and was subsequently executed. The extract may have some relevance to current affairs.
While [Kostov] was being tried, an orgy of meetings was organized throughout the country, at which everyone called Traicho Kostov the most disgusting names. In the hospitals we were driven from our beds to attend meetings which ended with the chanting of demands for 'Death! Death!' Few things have filled me with greater horror and revulsion than these orgies of human hatred and vileness. And the Bulgarian newspapers which at the time poured their rivers of filth over Traicho Kostov never found the slightest courage to apologize later. [...]
I had the feeling that [the activists'] violent hatred of Traicho was for them a personal organic necessity. They had this need to hate, and Stalin satisfied it. When the news of [Traicho's] hanging was announced, there were some who started dancing. An insignificant doctor, who within a year would rise to be the head of the government hospital, walked along the corridor of the sanatorium declaring that this was the happiest day of his life. This was no fanatic madness, but rather a necessity dictated by his servile instincts.
For it is noteworthy that all these comrades hated Traicho Kostov publicly. They hated him when others could see and hear them. They hated him because such hatred was richly remunerated, it was rewarded like a heroic deed. Do not think that the great majority of them believed in his guilt. [...] I could see that they knew Traicho to be innocent, but they seemed to be engaged in a mad competition in which everyone lied to everybody else claiming that he was guilty. The 'enemy' mania raged with a murderous force. Perhaps many were intoxicated by it because it liberated them from all human inhibitions.