There must be more to this story than is being said.
Maybe the Captain should have taken a look when the argument started, that would have been the end of it.
Cabin crew are good for reporting things and are always involved with CRM concerning things like this and they should be.
But since when are they taught the limitations of snow, ice or frost on the wings?
When in doubt, check it out, but if both pilots had visually inspected these wings and found them within limitations, would have been discussion over.