It's not arbitrary to draw the line there, although it may be hard to argue for making it a line.
I eat meat, but I do feel it would be more ethically right to avoid it. In the same manner, it would probably be more ethically right to not buy/drive a car, not use cell phones (conflict minerals), give more to charity etc. (So where do you draw the line at how much of your own money you get to keep for yourself?) Something can be ethically bad even if we do not draw a line in the sand (or, even if we do not as a society deprive someone of the freedom to do those bad things).
If I were a vegetarian, and drew the line at eggs or whatever, I would be drawing the line because a line would make it possible and practical to live as a vegetarian. (Similarly, the law has to draw a line somewhere.) Nature doesn't draw the sharp lines that our human languages do, but that doesn't mean we can't rank actions in terms of more or less ethical, it just means it's hard work.
I eat meat, but I do feel it would be more ethically right to avoid it. In the same manner, it would probably be more ethically right to not buy/drive a car, not use cell phones (conflict minerals), give more to charity etc. (So where do you draw the line at how much of your own money you get to keep for yourself?) Something can be ethically bad even if we do not draw a line in the sand (or, even if we do not as a society deprive someone of the freedom to do those bad things).
If I were a vegetarian, and drew the line at eggs or whatever, I would be drawing the line because a line would make it possible and practical to live as a vegetarian. (Similarly, the law has to draw a line somewhere.) Nature doesn't draw the sharp lines that our human languages do, but that doesn't mean we can't rank actions in terms of more or less ethical, it just means it's hard work.