They dont need to be public—a roomful of aristocrats are exceedingly unlikely to submit to collective obliviation, and there are enough people and enough factions present that anything they all hear is not going to stay secret.
There are tradeoffs here—he can spill the beans on the dementors and the true patronus and probably come out with his reputation strengthened if he plays it right, - Patronus the dementor in the room out of existance, and then letting the wizengamot “compel” an explanation out of him would be wieved as the wizengamot shooting itself in the foot, so that leaves hims smelling like roses.
Escalating the strategy of “Tell the wizengamot things they dont want to know” beyond that is going to make him very unpopular very quickly, as the wizarding world is very heavily committed to information control, but it is an option.
They dont need to be public—a roomful of aristocrats are exceedingly unlikely to submit to collective obliviation, and there are enough people and enough factions present that anything they all hear is not going to stay secret.
There are tradeoffs here—he can spill the beans on the dementors and the true patronus and probably come out with his reputation strengthened if he plays it right, - Patronus the dementor in the room out of existance, and then letting the wizengamot “compel” an explanation out of him would be wieved as the wizengamot shooting itself in the foot, so that leaves hims smelling like roses. Escalating the strategy of “Tell the wizengamot things they dont want to know” beyond that is going to make him very unpopular very quickly, as the wizarding world is very heavily committed to information control, but it is an option.