Generally, when people see us speaking up for animals, they want to suppress us as soon as they could. They are willing to step hard on animals with not even an eye blink.
In Buddhism, they believe an outcome or consequence one has now is from his past cause. For instance those farm animals had wrong/bad deeds in the many past lives that brought them to this horrible condition in the farm. That we cannot do a thing for them to change their life, that they have to pay for what they did in the past.
My question is what you (yourself) will tell those people in order to help animals, in term of Karma.