I think it
can be a tool to hurt others, and is often used that way by people who probe and learn our psychological weak points, but its proper role is to defend against ideas/culture that one
doesn't like.
If some new idea or trend is painful or apparently harmful or even just mildly annoying then it's important to try to understand why and to articulate this in order to protect one's mental integrity. This can be done in private. If one is defending against the actions of another, it may or may not be necessary to communicate the criticism to that other person. Often it is sufficient to silently note why their actions are wrong. (And if one fails to accomplish this, perhaps the actions weren't bad after all. Thus a failed attempt at criticism has changed one's mind about something. This is useful and important.)
Sometimes the criticism must be communicated, perhaps even in the presence of witnesses. This can be hard.
Public criticism is a different matter. There one is trying to protect a subculture from some idea or work that one considers harmful. I'm not sure what are the proper conditions under which to give this or hear this kind of criticism. Perhaps one has the right to be heard only if one can advocate an alternative approach or artwork that is worthy of attention. Or if one has made significant personal contributions to the field.
Note that this comment is a criticism of criticism as it is generally understood and so it makes sense by its own terms. Most of us and most ideas have been the target of unjust criticism at one time or another.