This is not a light issue for many reasons. The first thing to consider is that publishing that an organization is not reliable without knowing exactly who will read it, is for sure Lashon Hara.
Nothing in this world is black and white.
For a person living in Timbuktu, that doesn’t have access to Badatz and Velove products, the OU is perfect. For them to only eat from the highest standards is inconceivable. (think people on shlichus or someone newly observant.)
For somebody in Yerushalayim, New York, or Monsey, for instance, with a strong Jewish background there may not be an excuse to eat something with a simple OU.
I actually know of somebody who called up the OU to ask about a specific cereal. The Rabbi there asked her where she lives, and when she replied Williamsburg, he told her, “Shame on you. You live in a place where the highest standard of kashrus is available. This cereal was not made for you. Go buy a Jewish brand.”
The OU is a tremendous organization, providing the world with kosher products, but because of their tremendous size, it is very hard to have a mashgiach tamidi at every single plant. That is why mistakes happen.
I have respect for the OU, although I do not eat products with only the OU hechsher. Given my current situation in life, I have access to more careful “mashgiached” food, but i would never make away with the OU, and neither should you.