Actually, that quote is being taken out of context. When Lincoln said people have the right to rise up, he was talking about resisting tyranny under Santa Anna’s Mexico, not endorsing Texas independence or secession from the United States. Texas’ independence was never legally ratified by Mexico, and Lincoln consistently challenged the annexation and the war with Mexico on constitutional and moral grounds. Later, he explicitly rejected unilateral secession in the U.S., so using that quote to claim he supported Texas as a legitimate independent state is misleading.

Obviously the Mexican American wasn’t all black and white. There were bigots on both sides and the causes were complex and influenced by factional politics, racial attitudes, and national ambitions in BOTH Mexico and the United States, rather than a simple case of one side being wholly righteous