Animals are very much like us. They feel, they think, they form relationships, they mourn, they get stressed, they play, they get excited, they play tricks on each other and can be spiteful and get angry. All of the reasons we abhor cruelty to people apply to other animals also.
Apart from the ethical reasons for opposing exploiting animals for food and fibre, eating them can be harmful for health and is not required in any modern society. Factory farms in particular pose a serious health risk to humans as well as being appalling for animals. The health risks from factory farms aren’t just in the products they produce but in the real potential for spawning more pandemics like the 2009 swine flu which killed 284,000 people globally in it’s first 12 months. Unlike normal flu, 80% of the victims were younger than 65.
Animal agriculture is also a major contributor to climate change. The extra land required to farm animals and, more importantly to produce their feed is urgently required to be reforested to draw down carbon.