Your situation is a very common case in current scientific publishing. At the moment, pressure on scientists is much higher than it was in the past. Citations are one of the many measures of scientific excellence ( http://dx.doi.org/10.1371/journal.pone.0153730 ). Hence, everyone wants to obtain citations for their work.
In the past 5 years, I have encountered very similar situations as you did. Reviewers requested me to cite their papers (2-3 papers max), etc. Usually, some citations were not totally relevant. Nevertheless, I have never complained to an Editor or Reviewer but just cited Papers, and that's all.
However, defining your situation is much more complex than is seen at first sight. It would be good if you could specify if these 16 papers were authored by the same researcher or not. In line with this, it would be good to know if the references belong to the same journal or even journal families.
Anyway, we can outline some possible scenarios why someone would like to see 16 more references (relevant or irrelevant) in your paper.
Personal benefits: Each Reviewer sees reviewing a paper as a chance to put some citations in that paper. In this case, the Reviewer obtains some valuable citations easily (let us propose that 95% of authors cite recommended references in order to avoid any complications and quick
acceptance). Additionally, it is also intended to promote his/her work.
Raising the Impact Factor of the journal: Some years ago, The Scientific World Journal (TSWJ) lost its Impact Factor, since this journal was used as a resource for boosting citations to other journals. If I remember correctly, there were some Editors that were also Editors in other journals and they requested to cite references of other journals in TSWJ papers.
Citation cartels: The last point is citation cartels. Roots of cartels can be found in points 1 and 2, but are more sophisticated and organized. In simple words, a citation cartel is actually a group of "friends” or group of “researchers" that work together for mutual benefit. This benefit is manifested in personal benefits (to raise citations to each other) or to raise Impact Factors of journals. There are many scenarios of cartels: http://journal.frontiersin.org/article/10.3389/fphy.2016.00049
What to do in your situation?
Go with the flow: Just cite these irrelevant references and the paper will probably soon be accepted.
Talk to the Editor: You can write a message to the Editor and try to present your situation. A good Editor will understand your situation fully. On the other hand, be aware that the Reviewer and Editor may be also friends (Cartel members) and your email will not the save your situation.
Withdraw your manuscript and try in another venue: If you think that these irrelevant references will decrease the quality of your manuscript, then simply withdraw it. However, you will lose a lot of time and the paper will undergo once again the first round of reviews.