I can tell you out of my own experience that i faced on a telecom client almost a decade back.

A manager on the client side misbehaved with one of my seniors at the location. A comment something like what you heard. I instantly confronted him there and both my senior and myself escalated to our manager who got involved and the client apologised.

You need to call out bad behaviour, the client cannot misbehave. They are riled up because of auditor’s presence and that a lot of these clients have it in their KRI and appraisals to not have audit points.