Earlier quoted context omitted.
How do you force a split when one part (Whatsapp) may not have enough revenue to sustain itself?
I can't answer your question but i think you should be more specific. Your phrasing obviously comes with the interpretation that if a split-up would bankrupt a part, it shouldn't be done. Why should this be taken into consideration? Secondly. It has value. A different party could invest and keep it going. Why is it important that it sustains itself?
Of course, if you just wanted to punish facebook by destroying shareholder value, or you're certain WhatsApp users will move to an FB competitor rather than to FB itself, you might not care if WhatsApp stays in business post-breakup.