YOU are the host. YOU say what can is acceptable and what is not. NEVER argue with guests. Give them 2 options: (1) you can stay, just the two of you -or- (2) you can leave and stay somewhere else. if they argue you can say that's fine, i will report you to the authorities. Or you can just lock them out, cancel their stay due to violating the house rules or breaking covid standards.
REMEMBER: YOU ARE THE ONE IN CHARGE AND CAN DO WHATEVER YOU WANT. Airbnb will not help hosts out rather; they help guests and will side with guests in most, if not every, situation. Hosts have even showed airbnb police reports and still airbnb will not help hosts out. just do what you feel is right and move on. Take Charge!! Good luck!