PhD Thesis: citation for common knowledge and high level summary
You are being a bit inconsistent here. The reason for the introduction is that readers may not know the background. It would be good for them to see some sources that will fill them in beyond what you say. Mentioning a standard text or similar might be enough.
You also have risk with the reviewer if you don't yield to them. They may have a lot of control over what they accept. Again, pointing to some standard material, would probably suffice. If not, they will hopefully tell you to say more.
While I think  you are probably correct about your interpretation common knowledge and the lack of requirements to cite it, the other factors suggest you should do so in any case.