I let kids come with colds, because I wouldn't be willing to close my doors (thereby losing pay) if one of my kids had a cold. I'll send them home for fever, diarrhea, vomiting, etc. but not a runny nose. Unless they were so miserable that they weren't able to participate or they were too much of a handful for me to do our usual routine. If they're that sick, they need be able to be home with mom or dad.

He should definitely validate your suspicions though, instead of acting as though he's the one who's been home all day and saw how he was. It's a small thing but if he'd taken you seriously it would have shown that he values your experience and how you care for his child. He opted to do the opposite and left you feeling undervalued and under appreciated.

His being dismissive was pretty rude, but if he thought you wouldn't let her stay with a cold I could see him trying to deny it. Doesn't make it right, but it's what happens.