They discriminate against most races that aren’t Nord. The Stormcloaks are regarded as heavily racist. The Thalmor are controlling the Imperials, but they are also aiding Ulfric Stormcloak. No matter which side you choose, you are always siding with the Thalmor. The Thalmor and the Empire are an oppressive faction that doesn’t care about Skyrim or it’s people. The Stormcloaks are defending their home land. Although they are pinned down by them now, they have the resources to win long-term. The Imperials actually stand a chance at defeating the Thalmor. In every Elder Scrolls game, the player is given the choice to aid the Empire.

It is believed that he doesn’t even know what he wants, but he believes that lying will lead to him being the king of Skyrim.

He will whatever he can to recruit more people. You can’t really understand why they believe in these things until you’ve heard all of the facts. Some of their moral decisions aren’t entirely clear. Both sides have their own philosophy and their own justifications. This tends to be a very political discussion and requires all of the facts before you make a decision.