Here is the categorization of each quote based on whether it supports the idea that the war was justified or not:
Justified
“Polk…declared, ‘[Mexico] has invaded our territory and shed American blood upon American soil,’ and sent the order for war to Congress on May 11” (PBS.org, n.d.).
Not Justified
“…Ulysses S. Grant…would later call the war ‘one of the most unjust ever waged by a stronger against a weaker nation. It was an instance of a republic following the bad example of European monarchies, in not considering justice in their desire to acquire additional territory’” (PBS.org, n.d.).
Not Justified
“The act was a questionable one. Many Northerners believed that Polk, a Southerner, was trying to gain land for the slaveholding South. Other Americans simply thought it was wrong to use war to take land from Mexico.”