If I were a vegan, (which I am not and never will be), and my goal was to convince meat-eaters to become vegan, here's what I should not do:
Tell people that meat is murder, and try to convince them on moral grounds and with all the brute force of my strict, stringent, wonderfully compelling logic.
Here is what I should focus on instead:
Convince people with the glow of my renewed energy. Seduce them with extremely delicious, beautiful food. Add my greens to their barbecue. Actually enjoy my own food and let them see my enjoyment.
You see, I am a not-quite-but-almost-vegan for the simple reason that I enjoy the food I cook for myself. I look forward to that wonderful Koshari, that intensely aromatic Chili Sin Carne, this excellent Curry with tofu and greens. I really like my oatmeal and my smoothie. And I'm truly sorry, but I just don't feel for the poor cows, even though I know I probably should. It's just not there, on an emotional, visceral level. Maybe that makes me a bad person, but the fact is I could not care less even if I tried real hard.
Forget logic and morality. People are rarely ever won over by those. Their experience is that meat tastes yummie and that society won't punish them for their creature comforts. And the simple fact is that experience trumps rational reasoning. It doesn't matter whether that seems unfair or illogical or just plain wrong to you. That's just how humans work. If you actually want to make the world a better place, instead of being comfortable on the moral high ground, you better start working with nature, not against it.
Let's assume that the goal is to reduce suffering. Then, turning 1% of the population into 100% vegans is way less effective than turning 30% of them into people who eat small amounts of meat.
It's also less catchy, of course.