Why are all meat diets frowned upon when all veggie diets are not?

I'm assuming you don't mean a diet that only includes types of meat, but a mixed one. We do need plants and meats, research the flexitarian diet.

The problem is more of a question of mass production, animals being abused and meats being mishandled. But if you look you will see there are people who are just as upset about commercial fruits and vegetables too. Search with keywords like

heirloom seed

sustainable

permaculture

grow local movement

Food is designed in such a way that you need a wide variety to be able to maintain your health. Omnivore does mean we eat from a variety of food groups, whereas carnivores are meat eaters and herbivores are plant eaters. Human beings have a different digestive system than a wild animal. An animal can survive on a carnivorous diet because that is how they are designed to live. Humans are not designed to eat that way due to the fact that we need more than just meat, or a high percentage of it to stay healthy. Too much meat in a human diet is hard to deal with and leads to high cholesterol which in turn can lead to heart disease among other concerns. That is why people need a lot of produce in their diet. Produce will flush out the negative things that meat can leave in your system, and also leave you a lot healthier. Technically, humans can do perfectly fine without meat in their diet as a lot of protein can be found in plant products, thus eliminating the need to eat meat at all.

An all meat diets mean taking a lot of pills to have a balanced intake of vitamins etc.

An omnivores eat both and IMO is the logical way to keep a balanced diet, and I don't believe vegan or vegetarian diets are as good.

I would frown on an all meat diet as I think it is unhealthy, a mental thing.

It is that mental thing that makes you judge as a healthy or unhealthy diet.

If you ate nothing but meat you would not last long. You cant get all of the nutrients your body needs just from meat.

But on the flip side, if you eat nothing but veg, you will be fine, because veg can contain all of the important elements your body requires to function.

Don't get the wrong impression, I eat meat everyday, I could never be a vegetarian. I'm Not saying anything negative about vegetarians... I just couldn't do it.

Vegetarians can be very healthy, getting all the nutrients they need from plants and legumes. Meat eaters on the other hand can't get everything they need. Besides that, meat is high in fat and cholesterol making it not as healthy. If somebody only lived off meat, they would most likely have high cholesterol, fat build up in their arteries and heart problems eventually.

Because you can get a full range of nutrition from vegatables (vitamins, minerals even proteins and some fats) while meat only offers a limited range of nutrition (mostly fats and proteins etc. You wouldn't be eating a well rounded and healthly diet on only meats.

mostly becuz of the animal acgtivists