I think that the term "hothousing" is usually meant to indicate an environment that is conducive to unnaturally rapid growth. If it were just rapid growth, that'd be fine, but I think the implication that the growth is unnatural is inherent in the meaning of "hothousing."
Now, if you're thinking of plants, most people would agree that there's nothing cruel or morally wrong with making them grow faster than they would do naturally. But when the word is applied to children, I think it has to be a negative thing.
