If a company publishes only papers that clearly advance its interests, but the research is sound and independently reproducible, does that bias really lessen the perceived value and quality of the research?
Fair academic criticism: We shouldn't publish this paper because it has flaws X,Y,Z. (usually followed by an opportunity for the researchers to address X,Y,Z).
Unfair and/or non-academic criticisms: We shouldn't publish this paper because: I don't like the author/authors institution. I don't like this approach, approach X is better. I don't like the conclusions.
The last is potentially relevant here. And yes, clearly the quality and value of research is reduced by filtering based on results you want to promote. Which well may be in a companies best interest, but there are sometimes difficult lines to draw - when exactly do you move from "promoting the companies interests" to "propaganda intended to mislead the public"?
The done thing is generally for the reviewers to suggest additional references to improve the paper. If any mention of related work is entirely missing, then that's another matter, but a reviewer thinking that the authors should cite a particular piece of work (e.g. the reviewer's own paper) is not normally something that could lead to outright rejection.
If the paper was bad it should have been rejected by the conference to which it was submitted. If the paper was critical of things Google does and it didn't like that, that's pure suppression. And, as you say, academic norms provide a period of rebuttal, it's unclear how much was allowed here.
Secondly there is value of having anonymous review in an academic setting, however it sounds like they tried to enforce that anonymous review for the company, which again doesn't serve the same purpose. People should be told exactly why decisions are being made so they can correct their mistakes in the future. If you aren't willing to invite someone into a decision making process, when a large portion of their research is in biases in institutional decision making, then you have got to know you're in for a bad time.