Having read the article but not knowing anything about the posts themselves, I think most of this thread misses the point. Clearly Microsoft knew it was hosting Gab and what Gab was. There's a troll argument that suggests Gab is just "free speech twitter", but of course that's not the case: I've been screenshotting the front page for months, from a random anonymous account, and every time I've done it the front page…
This seems to accurately describe "free speech twitter". All the content that would get people banned on twitter is displaced into sites like Gab and 4chan. The few occasions I've perused these sites supported this: there were lots of hateful speech against minorities, but a few instances of hateful speech against the majority. A very narrow minority were the latter, but as far as I could tell these sites upheld their commitment to freedom of any legal speech for all and didn't censor them.