I'm not standing 100% by this analogy, but the similarity is that in both cases someone, out of anger or spite, abuses a huge lever the society has to punish misbehavior just to ruin someone's day, but the lever has a good chance of ruining someone's life. This works for both "SWAT team" and "virality on social networks" as values of "lever".

> I can easily imagine cases where I would try to end someone's career.

In your example, it would be reasonable to object strongly - given that you had evidence that someone in law enforcement had a deep hatred, like if you "saw them unfairly {arrest, harass, ...} someone in the hated group". I'd still hope you'd try the proper channels first, but if they fail, this is a matter of public importance. But the kind of thing we saw here - in this RMS story and other public outrage stories - doesn't meet the standard of evidence you described.

(Also, law enforcement is a somewhat special case, because it's a position of privilege and power, when one acts with authority of the state. You definitely want to police people wielding this power aggressively, but you shouldn't apply the same aggressiveness to random folks doing regular jobs, like scientists or plumbers or programmers. Former is preventing abuse of power; latter is just destroying someone's livelihood through vigilante mob justice.)

So what I'm saying isn't "don't ever go after one's career", just don't do it if your reasons are that you are offended by something you read. Ruining someone's livelihood like this is one of the most extreme form of damage you can legally do to another human being; it's thoroughly aggressive act, and it should only be done in circumstances justifying it. Words alone almost never are.