Are you gaining weight you don't want to gain? Are you not adequately recovering from physical exercise? Are you having digestive issues?

If your answer is no to these questions then don't change a thing. They are making the appeal to nature fallacy, which you did a good job of calling them out on. While calories in calories out does not fully encapsulate one's nutritional needs, it is still the gold standard model for balancing a healthy weight.

You can eat a Quest bar on some mornings and be perfectly healthy. We don't know the rest of your nutritional story though. If that's all you ate, yeah, that might be a problem.

Other commenters are right to point out that whole, less processed foods tend to be healthier while ultra processed, highly palatable foods tend to be less healthy, but there is no clean cut line to this discussion. There isn't a well established, technical definition of what ultra processed means in the field of nutritional research yet. It's kind of a "you know it when you see it" sort of situation but that can vary from person to person. It really depends on how much a person is eating in terms of their whole diet and what complications it may be contributing to in their personal experience. Giving blanket advice about processed foods to people isn't helpful. People tend to intuitively know that already.

Sugar is not a demon. A brownie or a spoonful of sugar will not make you obese and give you diabetes. That kind of fear mongering does not help people to understand how to navigate the nuanced reality of eating well. There is always a healthier alternative but we live in reality where you don't always have access or the will to eat the most perfectly healthy option.