The Soul Society is a corrupted system. It depicts itself as the world's moral compass, the absolute power and unquestionable justice. It either submits or eradicates whoever disagrees with their goals

Tousen is blind and he could see more than others could ever see about the true nature of the Soul Society, but he never had a voice. If power and justice are corrupted, then you become the power and you create your own sense justice

It is not all about hate, it's about trying to make a change. Tousen claimed to pursue the path of less death, and he meant it, though in his vision death was still necessary. He needed strong allies to face the Soul Society and Tousen would have no success in life if he hadn't joined forces with Aizen

Tousen have a dream, a dream about a world that there can be true justice where murderers deserve penalty so that's why he knew he couldn't be part of this world of his and he accepted to be just a paw for Aizen's master plan

If we parallel this to reality, Tousen is far much more relatable to each one of us than we probably acknowledge. Our world is also unfair and men in power will often treat us as nothing but insects, small cogs for their huge machine of lies. You may not care for it, but Tousen would be fighting that fight for you

Also, yeah Tousen IS my favorite character, but nevermind that