Is it really? Not by definition but I'll admit that people often use doxing along with a call for vigilante justice. I wasn't proposing violence of any kind ... just that some people should be shamed using their real identity.
Note that this does not mean "do not take action", please, do so: Call out false behavior, but keep it limited to the behavior. Collect evidence if you think that criminal charges should be filed. Support the victim. Doxxing, as appealing as it sounds is not the right action to take.
Vigilantism violates the rule of law. Just like censoring someone who says something really bad (but only if it's "really bad" and something you shouldn't say, of course), you can't just cancel the democratic principles because it seems like a good idea. That is the exact reason why we have these principles; because often it seems like a good idea but you will screw up if you make a habit out of it.