Wholeseller told my seller their house was worth 90k less smh

[Rod Desinord]

I recently had a seller come to me and say that during the process of deciding whether or not to put their house on the market, they entertained one of those Bandit signs. A wholeseller came over and told them their house was worth 90k less than what I told them it was worth when i previously visited them. Armed with this information they went nuts on the guy for lying to them. Subsequent appraisal afterwords confirmed my original CMA was correct. My question is how could this have been avoided if you are that wholeseller looking to make money.