The definition of a loophole is "an ambiguity or inadequacy in the law or a set of rules."

Carrying forward business losses as a deduction in future years is not a loophole, it's a purposeful and inherent part of the system for taxing business income. 

You can claim the system is flawed and should not permit this all you want; that's fine, although we'll disagree. But this is, objectively, not a loophole.