I only eat chocolate from small suppliers, and my main motivation for this, I have to admit, is that it's vastly better quality. I used to be in the habit of grabbing a cheap chocolate bar, but the quality of chocolate produced by the big companies that make most of the cheap chocolate in the UK, where I live, has deteriorated so sharply that I can't stand the stuff now, and many of my friends feel the same way. Chocolate made by small fair trade firms is more expensive, but not THAT much more expensive.
Now to your link to the article that says chocolate is "on track" to go extinct, but the good people at Mars are helping to save the world's chocolate supply by funding development of GMO cacao trees.
To suggest an answer to your question about the impact that one massive multinational controlling the development of the world's cacao trees might have on human trafficking...
WHAT COULD POSSIBLY GO WRONG?