i think that it is bad form to bring a cold anywhere public, let alone into a roomful of singers. Sometimes, I know, it can't be avoided and then the carrier should be taking precautions to try not to spread the illness, but there would appear to be absolutely no excuse for inflicting it on a social group.

No hero as far as I'm concerned, more a Typhoid Mary. Downright selfish - no-one is that indispensable to the group that they can be pardoned for spreading their germs!