Philip Wollen, the guy who made the quote, is a wealthy ex-banker who became vegan after retiring from Citibank and set up the Winsome Constance Kindness Trust with the mission statement "to promote kindness towards all other living beings and enshrine it as a recognisable trait in the Australian character and culture". So I'm guessing he believes all animals are sentient.
To the guest: We infect and kill animals for scientific research. Give them an illness to a dozen rats and cut one open every day to see whats different, that type of stuff.
"Every mammal on this planet instinctively develops a natural equilibrium with the surrounding environment but you humans do not. You move to an area and you multiply and multiply until every natural resource is consumed and the only way you can survive is to spread to another area. There is another organism on this planet that follows the same pattern. Do you know what it is? A virus. Human beings are a disease, a cancer of this planet. " - Agent Smith from The Matrix
I thought of this yesterday, but was out of comments. You folks may want to skip to around 1:25, but it's all good stuff.