> zero indicating when things might freeze is useful
Of course it is, parent is being silly.
Picking some other non-zero random number for freezing just seems absurd to me. But that's because Centigrade is what I am familiar with.
Say pick freezing = 12, or 47?. If those numbers for freezing seem absurd to you, then consider that the only advantage that "32" has for you is that you're familiar with it. People will find reasons to defend whichever one they grew up with.