There's no way they could plausibly determine this in the time they have had. And, there's no way there aren't people at google who don't agree with him. Which is why they had to act.

The key to large organization management is control: they are doing this quickly before anything else happens. His presence both legitimises his point of view, and acts as a rallying point. If others are sufficiently emboldened, they may also act out. If they start organizing together, this has the potential of rapidly turn into a long standing issue for google.