Most areas around the world are supplied food through small holdings. Many places on earth cannot grow just vegetables and grain to feed their population. Especially the northern countries and arid countries. It is easy to be a vegetarian if grocery stores are easily acccessible and one has the funds to pay for suppliments needed, there is no way to get heme (digestable Iron) from plants or vitiman Bs...Strict vegans need supplements or they become sick. Vegetarians can eat eggs and other animal products depending on the diet they follow. not getting enough heme, (anemia) for children and women is dangerous, it stunts growth and causes painful menstrual cycles, pregnancy issues, and breast feeding. We cannot absorb plant based iron, it is a fact...

Also if the world stopped eating domestic animals we would lose our hardy heritage livestock put the world in danger of famine if our corporate food grids fail...they are fragile because of their dependency on our energy grids and subject to infectious diseases from the use monoculture, chemicals, and crowding.

anyway, as you said there are far worse things we can do....lying, stealing, greed, murder, consuming more than we need....