It really depends on the criticism. I remember when I used to hang out on “left” twitter, on occasion I’d see stuff where it was like telephone game style personal spats that were impossible for an observer to follow and understand, and so it was more just the kind of conflict that might have been resolved with a proper sit-down and mediator, or at least clarified better what the problem was.

This case is pretty clear though just from reading the one tweet itself. It’s a problem of ideological line and that’s something we do need to crit in each other. Otherwise, we’re just doing the liberal thing of going along to get along:

To let things slide for the sake of peace and friendship when a person has clearly gone wrong, and refrain from principled argument because he is an old acquaintance, a fellow townsman, a schoolmate, a close friend, a loved one, an old colleague or old subordinate. Or to touch on the matter lightly instead of going into it thoroughly, so as to keep on good terms. The result is that both the organization and the individual are harmed. This is one type of liberalism.

https://www.marxists.org/reference/archive/mao/selected-works/volume-2/mswv2_03.htm

Self-criticism is common practice among MLs:

Wells: Unfortunately, I have various engagements to fulfil and I can stay in the USSR only for a week. I came to see you and I am very satisfied by our talk. But I intend to discuss with such Soviet writers as I can meet the possibility of their affiliating to the PEN Club. The organisation is still weak, but it has branches in many countries, and what is more important, the speeches of its members are widely reported in the press. It insists upon this, free expression of opinion – even of opposition opinion. I hope to discuss this point with Gorki. I do not know if you are prepared yet for that much freedom . . .

Stalin: We Bolsheviks call it “self-criticism”. It is widely used in the USSR. If there is anything I can do to help you I shall be glad to do so.

https://web.archive.org/web/20240425185930/https://www.newstatesman.com/long-reads/1934/10/h-g-wells-it-seems-me-i-am-more-left-you-mr-stalin

Unprincipled criticism, backbiting, etc., can be a problem:

To indulge in irresponsible criticism in private instead of actively putting forward one’s suggestions to the organization. To say nothing to people to their faces but to gossip behind their backs, or to say nothing at a meeting but to gossip afterwards. To show no regard at all for the principles of collective life but to follow one’s own inclination. This is a second type.

But strong unity of the ML kind is forged by working through problems, not paving over them with social niceties in public while holding onto resentments in private (that’s liberalism).