The closest description I can think of is a "drama queen/king", except that tends to describe people who like being in a drama.
Instead, I want a phrase describing people who like to pick up on stories such as the following:
- questionable decisions of others
- immoral acts
and then they get on their soapbox and passionately rant, uttering phrases like "it's disgusting", "it's a joke", "anyone who agrees with them should be ashamed".
Perhaps the descriptive term for that person might need to include that they are often immune to reason on subjective topics, and that the rants cause displeasure in the listeners, since frequent rants can wear listeners down, as the tone is loud, highly opinionated and of a very negative nature.
The reason I ask is I want search terms to Google to find techniques for dealing with such a person, and protecting one's self from their effects.
Edit: it is not really about whether someone finds faults in others, but the manner in which they frequently rant about issues, either in others, or institutions, or the nature of things.