The best we can do is strive to minimize the amount of harm we cause by living. We need to eat in order to live, and there is no moral or ethical code that dictates that we should refrain from eating and allow ourselves to die for some higher purpose.
Animals are not ours to eat, wear, experiment on, use for entertainment or for any exploitative purpose.
Welfarists are concerned with the quality of the animals' lives before or even during their slaughter and want animals to be treated, and slaughtered, "humanely." Welfarists don't necessarily feel that it is wrong for humans to use animals for our own purposes.
