I mean there's going to be discovery and depositions so "arguing" an after-the-fact justification is kind of pointless.
Also New York Post already reported that the FTC had documents suggesting the Instagram purchase was to take out a competitor.
>At the center of arguments to block the deal — made by then-FTC Chairman Jon Leibowitz — was a document the FTC had uncovered by a high-ranking Facebook executive who said the reason the company was buying Instagram was to eliminate a potential competitor, sources said.
“It was a spectacular document,” one source close to the situation said, declining to say whether Facebook CEO Mark Zuckerberg himself had written it.
https://nypost.com/2019/02/26/facebook-boasted-of-buying-ins...