All or nothing? I'm sure that will change the world for the better.
If you really cared about the problem at hand, you would be willing to take any help in the right direction-- even if that means just eating less meat than normal. You can't make a positive change with a negative message and you certianly can't ostracise an entire group of people(vegetarians) because they don't adhere to your own set of moral guide lines. That's the christian way, not the atheist way.
You may not believe that lacto-vegetarians are not vegiterians at all, but have not explained what is so special about being vegitarian at all! Very ancient Indian sages have told that the plants too have souls and even Aristotle also believed this. So, whether you kill an animal or fell a plant, you are committting violence. As an atheist I do not believe in the existance of a soul but I do believe in life. One saying in Sanskrit language says, " Jeevo jeevasya jeevanam". One life is the sustainance of another life. This is the most fundamental of nature's law of interdependance of life on this planet. So, vegetarianism is as good, or as bad, as non-vegetariaanism.
If you do not want to eat nonveg food, it's ok, but I am a plant lover so I appeal to you not to use violence against plants and stop eating veg food too. You may eat whatever else you please!