Opinions have points of view. Factual errors do not. Pointing out that someone writes a manifesto based on a complete misunderstanding of facts is far from a suppression of a viewpoint, especially when the assertions made are potentially harmful to the workplace not just at Google, but throughout the industry.
Another issue which needs clarification is the “freedom of speech.” This is not a universal construct. On the contrary, it is a legal construct, specifically related to the first amendment to the Constitution of the United States of America. Although it is arguably a concept which is present in other jurisdictions and should arguably be applied to legal constructs universally, it is truly a matter of legal permission. You are legally permitted, within some well established bounds, to say whatever you want. This comes down to one thing: that you are not guilty of a crime simply for saying things. What this does not mean is that you are free from consequences from saying whatever you want. One of those consequences may be getting fired from a job. Another one of those consequences may be that you are branded as an a**hole by a large portion of society.
Another thing that is not inherent to free speech: the freedom to be correct. You can legally say that the Earth is flat. You can say it, but you would be factually incorrect. You can legally say that women aren’t suited for working in the tech industry. You can say it, but you would be factually incorrect. Furthermore, you can also be legally fired from your job if making such ridiculous factual errors is inconsistent with the terms of your employment.
In conclusion, you are free to say that public criticism of the manifesto is suppressing a viewpoint, or that it violates free speech. You are free to say it, but by doing so, you are also incorrect.