This has been discussed repeatedly. And it seems very unfair to consumers in my opinion.
See
- How to write reviews and prevent defamation?
- Two years later my honest review got me a defamation strike?!
- German businesses abuse Google’s reporting tool - marks negative reviews as “defamation”
- Low rated reviews get taken down for defamation
- Be careful rating businesses in Germany
- Cafe keeps removing negative reviews, I keep proving that I was there, is there an end to this?