It isn't easy. The mind likes to take the experience of being right as an opportunity to also vent surplus emotion or aggression. To catch oneself doing this and forego the satisfaction is not something we do instinctively. Surprisingly, though, the trivial genre of internet comments turns out to be a good place for practice (and lord knows we can all use it).
I know these moderation comments can easily sound like "everybody please be civil and courteous", but that's not where we're coming from. Closer would be to say: be responsible for your shadow.
It's an open question how to process enough of one's shadow so that pure anger can cut like a sword in a clear way when called for. Most of us have work to do before we get there.
[1] more on 'demons' here: https://hn.algolia.com/?dateRange=all&page=0&prefix=false&so...