[[:Category:Ice cream]]
While I have not reverted your edit to the category tree, I believe you were in error in removing ice cream from the dessert category, as ice cream is nearly always classified as a dessert, is mentioned as a dessert in the definition, and appears categorized this way at Wikipedia.
A dessert is any food that is eaten at the end of a meal. Thus, any food that is eaten like that is a dessert. If I eat steak after a meal, then steak is a dessert. So dessert is not a good way to categorise foods as it contains things that are typically eaten as desserts. But you probably know that this can vary widely by culture. Pancakes are eaten for breakfast in the US, while in the Netherlands they are eaten as dinner, for example. So I think that the category "Desserts" is too vague and should be changed into something more objective and culturally independent.
If you truly think that, nominate Category:Desserts for deletion, or discuss it at the beer parlour.