The impact factor is what, 3-year moving average? 5-year moving average? Cite something that is 17 or 20 years old, let them have it.
I wonder, though, if you can find any suitable wording in the Ethical Guidelines of the American Statistical Association, say, that would indicate the editor stepping over them. Article A.10 requires
Disclose conflicts of interest, financial and otherwise, and resolve them. This may sometimes require divestiture of the conflicting personal interest or withdrawal from the professional activity. Examples where conflict of interest may be problematic include grant reviews, other peer reviews, and tensions between scholarship and personal or family financial interests.
If the editor is paid more for the greater impact factor, or is more likely to get promoted, then of course this constitutes a clear conflict of interest. This is not as ridiculous as it sounds: if editorship of a prestigious journal is considered to be a part of the service component of a university professor evaluation, and the said editor claims in their annual report that the IF of the journal went up last year, and finally that on the basis of this claim the professor gets their annual raise, then the causal chain does link the greater impact factor with money.
Articles H.4 and H.5 state:
Support sound statistical analysis and expose incompetent or corrupt statistical practice. In cases of conflict, statistical practitioners and those employing them are encouraged to resolve issues of ethical practice privately. If private resolution is not possible, recognize that statistical practitioners have an ethical obligation to expose incompetent or corrupt practice before it can cause harm to research subjects or society at large.
Recognize that within organizations and within professions using statistical methods generally, statistics practitioners with greater prestige, power, or status have a responsibility to protect the professional freedom and responsibility of more subordinate statistical practitioners who comply with these guidelines.
So the editor, being in the position of power, has this responsibility to protect your professional freedom of citing whatever you consider relevant. You, however, also have the ethical obligation to expose the corrupt practices... which you are doing here on this website, and I commend you for reaching out.
I think it is appropriate to send an email to the leader of whatever professional organization you expect the editors to be members of, and inquire whether the request for citations would constitute a breach in the ethics. Knowing a little bit about how ASA works, I can help you identify the relevant person.