The guy is an idiot (or worse).
Same scenario. Went into an appointment with a slightly scratchy throat informing my partner on arrival. It had developed an hour or two earlier. No problem he said. Had a great session! Love My throat was fine by the following morning (although my But was a bit tender). Several weeks later I get an obscenity laced call from the guy blaming me for two weeks of income he lost due to strept throat. I guess the apparent status of his immune system didn’t matter.