Obviously the reason for this ad campaign is because of recent political events, such as the proposal of the Green New Deal and Alexandria Ocasio-Cortez's demands on cows in regards to climate change.
As for the message it sends... I think I know what Burger King is trying to get across, but at best, the messaging on their part seems very poor. Unfortunately, we all knew that at some point, as climate change became clearer and clearer to the public, there would be some sort of clash between trying to improve the environment while fast food still remains popular to numerous Americans and others in developed countries. As we're all aware, fast food came around, really, and also had its popularity take off, in the 1950s, when cars, following World War II, became an easily attainable way for people to get from place to place. Of course, that same decade, at least here in the United States, saw the administration of Dwight D. Eisenhower spearhead the interstate highway system (based on what Eisenhower saw from the Autobahn in Germany while serving as a general in WWII), which only hastened this seeming need for fast food as now, Americans could travel between states and cities with relative ease. Unfortunately, a lot of this can be blamed not only for making climate change worse (which arguably has only worsened so much since the '50s), but also being the reason why obesity is now an epidemic. I guess it could be argued that not all was bad, though-newfound interstate commerce, after all, was how segregationist laws in the Southern states got struck down by the Supreme Court in the following decade in the '60s.
I'll admit to being a regular fast food eater, but even I am aware of the issues surrounding it. However, steps like these aren't going to solve a lot of issues surrounding fast food, such as being the reason obesity rates are higher among the poor, at least in the US.