If the answer is 'yes', then we have to reconsider our relationship with them if we consider ourselves to be compassionate. Economics and market forces determine how many people are employed in any particular industry. Vegetarians do not set out to put farmers out of work. If the demand for a product goes up that industry will employ more people. If demand goes down, fewer people will be employed.
Humans are omnivores.
In terms of evolution this may have given humans an advantage. It allowed us to eat a wider range of foods and so improved our chances of survival. However, to argue that humans have to eat meat because of physiology is a different ball game altogether. Modern styles of living allow us to eat all sorts of fresh food from all around the world. This means we can easily get all the nutrients we need from vegetarian sources.