I have seen organizers of different workshops in machine learning making it mandatory to cite their papers. This is totally fine if it is base paper or paper describing the dataset. But sometimes they even ask the researcher to cite non-relevant papers, they might be relevant in very broad term, for example, my topic and their paper is related to machine learning and every thing in content is different. How to deal with such a situation as I dont want to cite those papers because they are not related to my work.
Requesting citations as a quid pro quo for paper acceptance, or for in-kind citations, is highly unethical. Acquiescing to such a request is also unethical. I would avoid -- like the plague -- any conference where this is practiced. I would also report it to the conference organizers. Taking part in this kind of thing will make you look bad and could actually land you in trouble.
Here is an introductory reading list if you want to know more: