Taxation Law Conundrum

I'm having a major brain block with Section 43B of the Income-tax Act, 1961. So, apparently, a company can set off losses from a business against profits from a profession, but only if both are carried on by the same business or profession. But it gets worse – if the company has a separate business and profession, the losses are allowed to be set off, but the profits aren't. Is it just me or is this a recipe for double taxation? I mean, think about it - you've got losses in your main business, but you can't set them off because you've also got a separate profession which is profitable. It's like the law is trying to confuse us. Am I missing something, or is this Section 43B really as convoluted as it seems?