I'm a vegan. I abstain from eating any animal products.
Well I applaud you. I don't have the discipline for it. What types of health benefits does veganism bring?
If you eat a well planned vegan diet, it can reduce the risks of certain types of chronic disease like heart disease.
That's a good benefit, but what about with respect to the GI system? I imagine it would keep things pretty...regular, right?
I don't have any issues. Veganism is also acceptable for all stages of life including during infancy and pregnancy.
Why do you think people who are vegan are usually so insufferable about it? You obviously aren't, but I'm just asking in general.
I guess it's an ethical thing. People abstain from eating animals and it makes them feel better than other people. 
That air of superiority turns a lot of people off from veganism I think, because people start to see it as a culture rather than a set of dietary choices.
I completely agree. Vegetarians or people who just don't eat meat but eat other animal products, are a little better about it.