What’s so wrong with “umai?”

My 5-year-old daughter picked up the word "umai" from one of her classmates a while back and came home using it in place of "oishii." My Japanese wife got super mad at her for some reason that still doesn't quite make sense to me. Does "umai" have some sort of slang usage or something? Or is it just a matter of it being used more by men than women?

by Ok_Rutabaga_797