I completely understand people being grossed out by nose blowing at the table and agree that cloth napkins should never be used. That said, I have bad allergies. I'm usually okay, but there are days when I'm really really bad. I would make every attempt to go to the bathroom at a formal dinner, of course, but there are also times when, if someone insisted I go to the bathroom to blow my nose, we'd have to open a new thread about the etiquette of bringing someone's nice china into the bathroom to eat during a dinner party. I know it's unpleasant to watch someone blow their nose, and I agree that there are limits to what you should do (no honking, no leaving it on the table, try to turn away and not bring attention to it), but some of us really can't avoid it sometimes. Rest assured, we don't like it either.
I bet he'd really appreciate it if you leave tissues and a garbage can near his seat. Seat him in the back corner of the table, so his garbage can will be more discreet, if you want.
Mari, it's one thing to reuse your own tissues (I've done it too), it's another to use your dirty tissues on someone else!