You’re misreading that line. It’s: “This explains why TikTok succeeds, and why it is an app the United States ought to be concerned about. <continue reading post to find out why>”. The author subsequently explains why.
You mention that you get Fact A and Fact B. Fact C isn’t, “Therefore, TikTok should be banned”. Fact C, according to that post, is that China has begun ideological warfare. For supporters of a ban, Fact D then, is “The US should respond with defensive manoeuvres”. A ban is a defensive move. Nobody’s advocating for an offensive counter-attack (by running misinformation campaigns on their own social media platforms for instance). It’s perfectly reasonable to defend when under attack from a foreign entity.
Whether you think the US is under attack is the real question. But you said you agree with Fact B, so you agree that the possibility for China to use TikTok as a tool for ideological warfare is definitely there. The authors argument is that, combined with the evidence we’ve seen so far (censorship on domestic platforms, censorship on foreign platforms), maybe the US should be taking China’s own words on the matter more seriously.