Catharsis is good for the soul. It is confessions of fear, emotion, it is pouring out the pain of something that affects us. It needs to happen so that others are aware of problems.
It is not activism, though it can sometimes drive it.
Activism is being in motion, creating a working plan, figuring out how to workably change something without allowing our emotions to override the needs and rights of others.
When activism is overridden by emotional catharsis, bad laws are created and enforced for the best of intentions but with little true understanding of the potential impact.