I don't know... how can a "generational divide" possibly "flare?" A "generational divide" is an abstraction, an intellectual construct.
The author of the piece substituted an inanimate concept - which can't "flare," or do anything else - for one or both of a pair of human beings who can. McCain took the wrong side here, as elderly Republicans usually do, attacking one of his fellow party members from behind.
By making it sound like the "generational argument" is the issue instead of John McCain being the issue, the author took the passive voice, as I understand it.
Trust me. My high school English teacher went crazy if we used passive voice in an essay, (i.e. the voice used to indicate that the grammatical subject of the verb is the recipient and not the source of the action denoted by the verb.
Passive voice eliminates the need for a subject, which makes it an excellent tool for sleazy politicians who don't want to take responsibility for their actions.
For example: "Mistakes were made," rather than "I made a mistake."
Even when the subject is specified in passive voice (i.e. "Mistakes were made by me," rather than "I made a mistake), it is a very inelegant and stilted way of writing. It was a big no-no in Mr. Painter's senior English class.
For more info see: http://grammar.ccc.commnet.edu/grammar/passive.htm