Let me check that I have correctly understood the scenario you're anticipating.

1. Someone uses "volkswagen" as a verb meaning "cheat in benchmarks".

2. Volkswagen takes them to court, on the basis that it is slanderous or libellous to associate Volkswagen with cheating in benchmarks.

3. Counsel for the defence reminds the court that Volkswagen were in the news for a protracted period for a benchmark-rigging that saw them hit with a multi-billion-dollar fine, slashed a third off their stock price, saw their CEO resign, led to there being a "Volkswagen emissions scandal" page on Wikipedia, etc., etc., etc.

4. [THIS IS THE BIT I'D LIKE YOU TO FILL IN FOR ME.]

5. Volkswagen wins the case.

How exactly does step 4 go?

By volkswagen arguing that this is industry standard behaviour, and the entire media campaign is already libel and slander.

And they’d have a pretty good case with that, considering the original report all this media campaign was based on called out 6 carmakers, but the media (and the poster) only call out Volkswagen.

In the same vein as Adobe sues me for photoshopping a picture or Alphabet sues me for googling my exgirlfriends' names?

No, but you don’t wanna get sued for libel and slander. If VW can realistically show that it is industry-standard behaviour (which is pretty obvious), then they might even have a chance to win.

Either way, it’d be expensive for you.

I'll call you when they sue.

It's been said, "Truth is the best defense for libel". Reasonably held opinion would then be the second.

Realistically, not mentioning anyone or anything is the only complete defense. The truth still comes close.

I do not think Volkswagen will try to sue you for adding a new phrase to urban dictionary ;-)