I agree, but at least nuts are high in unsaturated fats, which have some rather solid clinical backing as being healthy. Obviously still energy-dense, and if nuts are used a primary protein source it will likely be difficult to stay within a restricted caloric budget.
E.g. if you want to follow the government recommendation and have 20% of your calories come from protein, peanuts will fall short as only 18% of their calories are sourced from protein (79% from fat). 349 grams of peanuts (about 3/4 of a pound) has 2000 calories and 91 grams of protein - with 175 grams of fat.
I’ve always heard that peanuts were kind of the last option you’d want to pick among nuts, specifically because they’re so high in saturated fats (about 20% of the fat content). They’re not bad per se, but there are much better options.
Still, they’re a great source of added protein and unsaturated fats, but like you said, don’t rely on them as your primary source.
This is the first post I’ve ever heard that peanuts can be poisonous if overeaten, but I know that most tree nuts are. Almonds and Brazil Nuts are high in selenium and can straight up kill you. As few as 6 Brazil Nuts may be enough. Cashews are also slightly poisonous because the fruit they come from is.
You are definitely better of snacking on peanuts than, say, Doritos. It’s not that they are a bad food, they just don’t have a great macro balance if they are the major component of a diet. From this unvetted comparison they don’t seem to be too bad compared to other nuts.
If someone really wanted to get most of their calories from peanuts, they would probably want to supplement with something like pea protein powder and some high-fiber greens (or even beans). This would allow for keeping carbs relatively low while having a more even balance between fat and protein intake. Not quite keto, but not the typical high-carb western diet.