It’s an excuse to put troops into Mexico to support a coup.

What’s wrong with opposing cartels?

What’s wrong with opposing terrorists?

What’s wrong with opposing dictators?

The answer to all of these is: The western empire declares something/someone an enemy when it wants an excuse to attack it/them. If you take it at face value in a vacuum, it sounds reasonable enough, but historically, it’s almost never about what they say it is about. You can even see this sort of thing in the hundreds of years old colonial civil/savage narrative that lingers some today and the narrative playbook hasn’t changed that much, fundamentally. They’re still doing it to Palestine, for example.