While arguing may not be productive, I have had good results challenging Gemini on hallucinated sources in the past. eg, "You cited RFC 1918, which is a mistake. Can you try carefully to cite a better source here?" which would get it to re-evaluate, maybe by using another tool, admit the mistake, and allow the research to continue.

With this example, several attempts resulted in the same thing: Gemini expressing a strong belief that Github has a security capability which is really doesn't have.

If someone is able to get Gemini to give an accurate answer to this with a similar question, I'd be very curious to hear what it is.