That's pretty bad if Google did that tbh. Why even bother having a review system at all if the integrity of it is compromised.
I actually completely disagree. It is
these reviews that compromise the integrity of the review system. Taking them down is absolutely the right thing to do. I see it as similar to the "fake news" (as in actual made-up news, not the Trumpian form of "news I happen to disagree with"): Society expects these companies to disseminate accurate information (or at least provide their best endeavour).
Two cases that they need to be able to deal with are a company paying for positive reviews, or a company paying for negative reviews of a rival (or, more likely, an activist group calling for it). This situation is a variant of the second one. I'm pretty sure Amazon has programs in place to try and detect these kind of fake reviews, and I would expect Google to have them as well (though search online suggests they are not perfect). They would be considering signals like an unusual number of reviews in a period of time, unusual characteristics of the reviewer, etc.
I think this is completely different from a business trying to get individual reviews taken down because they don't like them. That is where some review systems have the opportunity for the business to respond, allowing the potential customer to decide between the reviewer's story and the business's story. That isn't an appropriate mechanism to respond here because the reviews significantly affect the aggregate, even for potential customers who don't read individual reviews.
EDIT: Should clarify - this to me is the ideal way review systems should work. I'm sure the reality is much more messy...