All advertising is incredibly political, because companies operate in a politicized world.

Under this guidance for example, Shell could advertise all they want on twitter, but running an ad against Shell about how they pollute the environment or contribute to global warming would be banned.

So then your options are to ban all advertising, or be selective in what advertising you allow. Which is inherently a political position.

I am not buying this, in the narrow definition, politics is relevant to politicians and elections. Shell is just a private company, so is fair game.

Secondly, suppose you could not advertise about shell so what? You can advertise for Greenpeace and related causes.

Greenpeace would absolutely be considered political and likely banned, considering the causes they advocate for.

Which, again, means companies like Shell could advertise all they want, but anything that calls them out would be considered political.

This is an absurd claim. Any charity advocates something, from planting trees to helping the poor.

One would have to have a purposefully obtuse definition of political speech to outlaw ads by charities but allow Shell.

Just because sometimes lines can be hard to draw, it doesn't mean they can't or shouldn't be drawn.

I don't disagree. I absolutely think Twitter should draw lines. It's just intellectually dishonest to try and get around it by banning all political advertising, but it's obvious because Twitter doesn't want to take a stance on anything. So they want to act like they effectively take a stance on nothing.

Twitter isn't drawing a line in the sand as much as they are deciding to ban the whole beach and kick everyone off it.

It's still not easy. Suppose I write a bot that flags all of my competitors ads a political?

At least then Twitter would have a pretty clear incentive to combat your bot as it and its ilk could have a substantial effect on their revenue. No doubt this will happen. You could already be doing this on youtube to flag a competitor's content as copyright infringement.

Well, Google has figured out how to make it really hard to make a link farm that gets your web page to the top of the listings.

Very similar problem. I would expect that they would keep track of who is doing the flagging and whether their flagging is consistent with other flaggers, and various other tests for "naturalness" and lack of bias and so on. Then weight things appropriately.