The opposite of love isn't hate, it's indifference.
sending damaging information to this woman's elders mostlikely won't have the results the OP is looking for. What then? Stepping up to something abit more intense and perhaps physical cuz she deserves to feel the pain he's feeling? No, this should be nipped in the bud at this moment before anything stupid and irreversible happens.
we're not taking about a corporate entity here. We're talking about an emotionally immature man who got played by an equally emotionally immature woman. Best just to cut all contact, move on and grow up.