While I am not familiar with the text Against Love by Laura Kipnis, but the Polemic essay is easy enough to describe.
Polemic offers differing arguments against an opinion, doctrines, or persons. This being said, a Polemic essay is one which the author offers their own opinions upon different controversies surrounding an opinion, a doctrine, or the ideology/theology of a person.
For example, one may not find the actions of the Westboro Baptist Church appropriate. Therefore, one would construct an essay based upon their disapproval of the group's opinions and theologies.
Another way to look at a Polemic essay is by renaming it. Simplistically, this type of essay is an argumentative essay. The purpose of an argumentative essay is one which
requires the student to investigate a topic, collect, generate, and evaluate evidence, and establish a position on the topic in a concise manner.
What one needs to do is simply take a stand against a controversial subject and explain their own stand.