His previous interaction has shown to him that McKinsey might not be a loyal contractor for the prospective contract. The way they treated him in the past might just indicate the way they would treat those hospitals. Since nowadays there is a thick competition for every contract, just the gut feeling of the person in the deciding position is enough to tick them off.

Besides all, he has the first hand experience dealing with them, and they acted unprofessionally. It would be irresponsible for him not to take that into account.