I think we share some ideas in our reaction to CW and modern factory farming but I think my main opposition to vegetarians and vegans comes from a different place.

There are a lot of high profile people in the vegetarian spectrum who are pushing for meatless diets to replace the CW diet as the healthiest. The last thing we need is another McGovern Committee run by vegetarians making it impossible to be paleo.

That is why I oppose their efforts publicly even if I might give them a few nutritional highfives privately. In the end the majority of vegetarians live on veggie burgers made from wheat and soy and those are the farthest things from paleo eating as i can imagine. I can't agree with proponents of those foods even if we share the very easy to understand common ground that eating vegetables seems like a good idea.

Ideally, at least, the Paleo diet depends more on science while the vegan diet depends more on a moral stance. If a Paleo person sends you a long video to watch it's probably going to be a Gary Taubes lecture, while a vegan will probably send you "Earthlings".

I think paleo and vegetarians can easily agree that the modern standard diet sucks for humans.

Presuming that the vegetarian choice is being made for health reasons, and not ethical ones, then we are matching groups of people who are just trying to improve our health levels. We just landed on differing sets of information, and then acted upon that learning.

It turns into a whole different thing when the vegetarian choice is being made for ethical reasons. Ethical choices are much harder to quantify as compared to evolution and biochemistry. Not a thing that will be settled anytime soon.

In summary, to each his own, and please pass me the grass-fed steak cooked in matching grass-fed butter.

When I first read the question I thought it was insane. But the poster gets me thinking about about how we connect to food. Vegans see things through this Panglossian lens, "all is for the best in the best of all possible worlds." In this idealized worldview, plants surrender themselves for our sustenance and cows live with wolves, and even the wolves take up grass. It's a fairy tale and a utopian vision.

When we contrast this with paleo, we see an analytical, scientific bent that appeals to a lot of people. Most people, I think, just want to be healthy or lean or cure disease. Or all three, really. They want to know what to eat in order to be healthy. A practical solution. Typically, any strict dietary intervention works wonders for people because it reduces processed crap food. People improve. This happens with both vegan and paleo diets, although paleo diets happen to be easier to implement in the long term and are more effective. So food becomes religion. I was blind but now I see!

And this can lead into a paleo fairy tale which is that "our" method is the only one that works, and it becomes dogma. But I bet if we examined the paleo diets of 100 regular posters here we would find, among the commonalities, many striking differences. Heterodoxy!

I'd like to think that the main difference between vegan and paleo is that heterodoxy is permitted and even encouraged. For the most part, I see that on this board and it's encouraging.

Another thing we have in common is how the diets work. There is a strong simple underlying principle that just gets applied to food.

You can get very detailed, but I can explain either how to eat vegan and how to eat paleo with a single sentience.

I think that, in addition to the focus on natural food by nature, gives us an underlying agreement and orientation that is different then the scatter shot nature of conventional wisdom.

My personal opinion is that vegans don't want to cause harm to another being. They say that killing an animal to eat it (even as humanely as we do the killing these days) is a violent act; which it is. And, might I add, that nature is a violent act. Those zebras getting eating by lions suffer. Nature isn't happy bunnies and butterflies. Nature is a violent, unrelenting bitch. They see that there are other things we can eat, which makes killing an animal for them to live is unnecessary. The problems arise when they go around spouting their "but is soooo healthy for you, eating animals will kill you!!!!" without any science to back up their claims.
When I meet vegans who don't eat meat because they don't want harm to come to another living being in order for them to thrive, I have no complaints. I'll keep eating my steak and uncured bacon, and you can keep scrambling tofu. I get my panties in a gigantic bunch when they start spouting off about how bad animal products are for us. Umm....we are the most prolific species on the planet because we stalked, killed and ate animals way back in the day. If eating animals is killing us, how did eating animals turn us into the species that dominates Earth?

Veganism is purely about morals and the belief that animals should be treated equally and not used by man for man's own needs. Some vegans take this as far as not using oxen to help sow the land to plant the next harvest and not using service animals for the blind. The dietary aspect is born out of that, not out of wanting to be healthy.

I had a discussion about this with a good vegan friend of mine and he pointed me to here for more information. http://www.abolitionistapproach.com/faqs/

I have always believed that mankind evolved eating animals, and if not for the ability to hunt, cook, and eat meat, we would not have evolved to where we are now. Some vegans would argue that if there were no animals, man would have found some other way to evolve to where we are now, but I highly doubt that. How else would we have gotten the levels of proteins and fat (fish oils!) that helped our brains grow to handle more complex processing?!?

Thus, I would say no, there isn't a similarity between paleo and vegan. Paleo is born out of evolutionary needs, whereas veganism is born out of ethical beliefs towards the treatment of animals. There might be a closer similarity between paleo and vegetarianism, but I don't understand a dietary movement that shuns animal meat, but says it's OK to eat their eggs and milk...

although paleo diets and vegan diets seem very different, I've followed both, and I consider them both healthier than the SAD diet

There is plenty of contradictory science to be found. You follow the science that you believe. Period. There are thousands of studies to support veganism. Just like the thousands of studies that oppose.