How about a thought experiment: in "communist bandits", replace "communist" with derogatory name for some other nation or social group.
In the case of communist bandits, it's a criticism of a political ideology, and in particular here one party. Criticism of political parties and ideologies is completely fine, even when expressing insults to them. Expressing threats of violence or other crimes isn't permitted or moral, but expressing dislike or disrespect is perfectly valid. Can anyone say they've never expressed disrespect to any ideology or political party in their life?
Does that offend you?
Would you be as happy to see fascism protected from negative commentary online, as you clearly would communism?