What an abomination.
The Oxford comma, so-called because the Oxford University Press style guidelines require it, is the comma before the conjunction at the end of a list. If your preferred style is to omit the second comma in “red, white, and blue,” you are aligned with the anti-Oxford comma faction.
The pro-Oxford comma faction is more vocal and numerous in the US, while in the UK, anti-Oxford comma reigns. (Oxford University is an outsider, style-wise, in its own land.) In the US, book and magazine publishers are generally pro, while newspapers are anti, but both styles can be found in both media.
This is a perfect example of one thing being correct and serving well for so long, for logical reasons but then someone who hasn’t a clue comes in and attempts to set up an alternative which is just plain grammatically wrong.
Along come pundits and identify two equal and opposite sides of a “debate’ when there is no debate at all. The false side, calling themselves pro-Oxford Comma are taken as a legitimate force, which they clearly are not – they are purveyors of something false.
For the record, the “and” between the penultimate and last item in a list replaces the comma. To have both is not only tautology but it looks ugly. Yes I know the Americans do it but one has to humour them – something went wrong in their past and they lost the ability to spell correctly and punctuate sentences properly part of the time.
A comma separates items in a list and is used for a pause. It is not a separator of main ideas or thoughts – the semi-colon, fullstop [period] or conjunction are for that. Let’s not get into relative pronouns here. The “and” and “but” are conjunctions. That means they join two separate ideas but are also used for lists.
In the separation of main ideas or thoughts, as they make the following idea either additional or contrary [see "or" as well], then logically, they cannot start a sentence in themselves. I know I do it for writing effect but am conscious that I’m breaking the rule every time. A conjunction cannot start a sentence, otherwise it is no longer a conjunction.
For those not unduly concerned about an Oxford Comma: