Is Buddhism a teaching of neutrality or "siding with the good"

In situations involving lies and/or violence, does Buddhism teach siding with the good against the bad, or does it teach neutrality i.e. staying outside the conflict and not taking sides? Specifically, If someone (knowingly or unknowingly) spreads lies or misinformation, should a Buddhist challenge them to defend the truth OR is it preferable to remain uninvolved (to avoid provoking a conflict)? If someone violently attacks someone else, does Buddhism teach fighting the aggressor and defending the victim, or does it teach staying out? Are there examples of such situations in the Pali Canon and later texts? I mean this question literally as written and am sincerely looking for answers - i.e. this is not a rhetorical question.