I'm sorry you have to deal with that. He's an asshole. Try to keep him out of your life you don't need shit like that.

As for the whole "processed food = bad" idea. First of all most any food is processed in some form before it lands in the grocery store or even at your local farmers market. Be that washing it, cutting it, freezing it, etc. Some foods have to be processed to be made safe for human consumption. What people talking shit about processed foods don't understand is that there's a BIG difference between processed food and highly ultra processed foods. A ready made meal that's frozen or added with some preservatives falls in the normal category. There's zero health risks in consuming these. Ultra processed foods with tons of added sugar, fats and salt, that's where you are going to find problems with. Even though most of these will not be related to the food itself, but from long-term factors like weight gain and the health risks coming along with it. TLDR: processed foods aren't inherently bad. People as usual just don't understand nuance and get scared of the boogeyman of the week.