Veganism is about equality, fairness and justice for everyone. However, the focus is on other animals because in terms of both numbers and degree of suffering, the greatest harm of non vegan living is inflicted on non humans.
When you choose to live vegan you tackle the issue of animal use at its core. The issue is not how we treat other animals while they are alive; it is that we breed them into this life for our use at all.
At its heart, veganism is about how we relate to others, ensuring that we live in ways that accord them the things we wish for ourselves, regardless of any perception of difference to them, or distance from them.