I don't believe you are entirely wrong, but your claim is lacking the full picture. First, the article was correct about myoglobin (the oxygen-carrying protein) giving dark meat its color. I was able to find information proving this claim that says myoglobin stores oxygen in muscle cells that can then be used for constant activity. Dark meat is composed of these muscles. You are also right in saying that white meat is a good source of protein, but I do believe you could have phrased your claim better. Dark meat also has its share of perks. For instance, in the article I found, "Benefits of Dark Meat," it says that there are many essential nutrients in dark meat as well as iron and zinc. There also happen to be "higher quantities of B vitamins, like thiamine, niacin, and B12." Which are very important for regulating metabolism. It is clear that white meat and dark meat are both beneficial in their own ways; it partially depends on what the person who is eating them needs. So instead of saying white meat is better, if you really want to call attention to the benefits of white meat, you could have said, "White meat is an excellent form of protein, and here's why."
https://www.chicken.ca/cooking-tips/the-benefits-of-dark-meat
https://annex.exploratorium.edu/cooking/meat/INT-what-meat-color.html
https://www.today.com/health/diet-fitness/white-meat-vs-dark-meat-rcna158792