A word describing the core point of a newspaper opinion column [duplicate]

In terms of graphic design, the text framed in red is called a pull quote, a common technique to break up large areas of text that also functions as a secondary headline to attract the reader to an article.

The relationship of the highlighted text to the article depends on who wrote it, which in most publications would not be the author of the article itself.

In this case, with only a single pull quote, it functions as an explanatory or summary subtitle:

Banning Books: A new form of censorship has emerged …

"A new form of censorship has emerged", is the essence of this article

"The essence of something is its basic and most important characteristic which gives it its individual identity." Collins

"The most important part or aspect of something: The essence of her argument is that the policy is wrongheaded." TFD