Instead of it meaning all of mankind is equal, it truly boiled down to: All white, rich, males in a position of power, are equal.
I think it's a no brainer why some resisted unfair treatment. If you, your family, and everyone else like you were being disrespected, and stripped of their rights, wouldn't you want to freaking do something? So slaves, women, etc rose up, and tried to resist.
Slavery has no place in "All men are created equal"
Deliberatly placing a divide between social classes is not "All men are created equal"
Refusing women the right to vote is not "All men are created equal"
Robbing people of their land is not "All men are created equal"