The Moral Efficacy of Lies

The video above has personally helped motivate me to adopt vegetarianism, my brother veganism  and several of his friends vegetarianism and veganism. My problem is that it does not approach the issue philosophically  and I counted many an outright lie. Is this moral to do whatever it takes to stop people from harming animals? Where is the line?

[One scenario I think of, which is used to justify some amount of lying  supposes you're house is invaded by several gun men. They're there to kill everyone in the house and they ask you 'Is there anyone else here?' Usually this scenario supposes your family is there, but suppose it was a herd of cattle in the basement they would not find otherwise, would you say there where? No you'd be justified in lying to them to preserve the lives of the cattle in the basement. (If they offered to spare your life in exchange it might be a different story, but supposing that's not the case)]