It's not just about whether Soros money went to groups that funded Facebook critics. Soros donates to a
lot of progressive groups, you'd be hard to find any single company/organization that have
not been criticized by a group that has ever taken Soros money. For example, Soros's Open Society Institute has made grants [0] to many media orgs, such as the Center for Investigative Reporting -- better known to HN readers as Reveal for publishing recent stories about unsafe conditions at Tesla. The very same Tesla that Soros himself has had a stake in [1] to improve its stock price.
So if Facebook wants to make a non-dogwhistling good-faith claim that Soros is attempting to profit from the destruction of Facebook, the burden of evidence is on them to make the case that Facebook is indeed being specifically targeted by Soros, in a way that say, Tesla isn't. If they had that evidence, and they weren't just trying to dog whistle for all the folks who think Soros is a Jewish globalist puppetmaster, then it raises the question of why they went through an intermediary who pushed anti-Soros stories through well known right-wing trolls?
To put it another way, a true fact about George Soros is that he is Jewish. Would you see any problem if Facebook funded a PR group to push news stories focusing solely on the fact that George Soros is totally a Jew? Or to use another example, how about if that firm pushed stories about how Barack Obama spent his early life living with a white teenage woman, another very true fact? [2]
edit: added link for the fact about Obama
[0] https://www.foxnews.com/opinion/why-dont-we-hear-about-soros...
[1] https://www.reuters.com/article/us-tesla-bonds-analysis/geor...
[2] https://www.nytimes.com/2011/04/24/magazine/mag-24Obama-t.ht...