>WhatsApp and IG _were_ alternatives
Are they though? They're nearly completely separate products with different activities and goals. If WhatsApp and Instagram were never acquired, I don't see them actually being very different at all from the consumer's pov, though I see them being less successful businesses without Fb's ad network and infrastructure.
I don't think these two are actually competition for facebook, facebook is fundamentally a communication tool built on top of your genuine friends and family social graph, it has no true competitors to speak of.
Facebook's acquisitions have provided them with two new business lines, one of which has been immensely profitable for them, but I don't think its actually affected the social media market. Social media companies built on different social graphs (ie. linkedin for your professional graph, twitter for a unidirectional follower graph) or a niche, fundamentally different interaction model (ie. pinterest) still can exist and thrive. I think facebook could or could not acquire any of these, and they're raison d'etre would essentially be the same.
Facebook's privacy concerns are real, and worth having a conversation over, but I think the claim that they have monopoly power over social media as a whole is false.
I don't think you'd do any good breaking whatsapp or instagram our from facebook. Instagram would have a rough couple years detaching their infra and getting a sales force, but it would remain the same. WhatsApp may die unless its given an enourmous lump of cash to fund it as it finds a path toward profitability, but without fb's ad network it will probably never be a great business.
Overall, breaking up Facebook in the way the article says wouldn't really do much harm, but it wouldn't do much good either. And I think its an abuse of antitrust power to simply not let a company be an industry conglomerate and have multiple successful business lines.