Well, unless he is demanding a whole new dinner, it's his to do with as he pleases. I wouldn't eat it either. I would be miffed, especially as I drill the coughing manners into ds and it was avoidable. He's just hungry and hacked off.
Yes it's his dinner to do with as he wishes...but perhaps a more tactful approach would have been best? She's only 6, and probably really hurt! I think it was out of order - but then I'm a softie and hate seeing children upset by adults. They see things so differently to us. Hope she's ok now!
Is your H someone who is particularly picky over food or squeamish about germs? If so, then there is some excuse for his behaviour; some people are really oversensitive about this sort of thing (and TBH generally sholdn't be allowed to eat in company and/or given a swift kick up the ringpiece if they start performing, anyway). If he isn't normally like this, then his behaviour is a nasty, spiteful, attention-seeking piece of bullying, meant to upset and guilt-trip a six-year-old far more severely than a moment's carelessness deserves.
FGS! You all live in the same house, you swap germs all the time. If she spat in his dinner it wouldnt mean he would be any more likely to catch anything. In our house you can eat anything, provided you get to it before the dog does. I'm a healthcare scientist BTW