This may seem obvious, but the implications are significant. If a vegan world really is our goal, we can't spend our time talking back and forth with other vegans about how great we are / how amazing veganism is. Rather, we have to convince more and more meat eaters to change their diet.
These are two very different discussions. Although many vegans care about the minutia of any negative health claim regarding meat, far-reaching environmental issues, and any and every connection to animal exploitation, this is simply not the case for the vast majority of non-vegans. Go to any McDonald's, or to a grocery store, or mall food court -- people aren't making their choices for optimal nutrition. They are choosing what is familiar, convenient, cheap, and tasty.
For all intents and purposes, modern animal agribusiness doesn't care about a handful of whole-food locavore hard-core vegans -- they know that although this is a profitable sidebar at Whole Foods, it isn't the future for the masses. And for every person who goes entirely vegan because of health concerns, many more give up eating large animals and start consuming many more smaller, more intensively raised animals.
What is a threat to entrenched interests are psychologically-informed campaigns that accept human nature as it is and work within our current system; e.g. meat reduction (e.g., Meatless Mondays) and cruelty-free foods that are familiar, convenient, cheap, and tasty.
To fend off the latter, there is a concerted effort by industry to attack soy, the basis for most veg meats. (Here is an article discussing one aspect of the war on soy.) It is a transparent ploy, but surprisingly effective -- aided by a subset of vegans who are quick to believe any negative claim about any food. If you know someone who has bought into the meat-industry's attacks, send them Ginny's summary and Jack's reply to one of the hatchet jobs on soy.
In the end, we each need to make a choice -- do we spend our time glorifying and defending our specific veganism (and any other food and political obsessions we insist on attaching), or do we do realistic work for a vegan world?