Thank you for this post! I'm a huge proponent of a communication tool (some call it a way of life, heh) based on a book called Nonviolent Communication (NVC) by Marshall Rosenberg. Anyway, some relevant principles of NVC that I dig the most are: (1) You are responsible for your own feelings and (2) Words only hurt you if you let them. Your example was actually quite close to NVC. NVC takes it even further. Example: "I hear you saying these things about MSP and I'm guessing you see some things happening that you get pissed off by because you value fairness?" See how I'm merely trying to hear/understand their perspective? No defense because there is no wrong. It's their issue so we "keep it on them". They might answer, "Yeah, you guys are total scammers!" But you don't give in to going down to their level. You continue to empathize. "I'm guessing maybe someone you care about got scammed or you heard of some scammy behavior, so you want to let people know about this?" See how you are merely [gently] probing and still not playing their game? 
Anyway, I could go on forever. Just wanted to thank you and say hi :-)