Commencement speeches are all about advice. The learned and successful use them to dispense wisdom -- and warnings -- to the next generation of leaders. And this year, many of the nation's commencement speakers have the same message for graduates: Be wary of Republican presidential nominee Donald Trump .

President Barack Obama cautioned grads on Sunday against embracing Trump's isolationism and ignorance . The past GOP presidential nominee, Mitt Romney, also made similar remarks during his commencement speech earlier this month.

"Demagogues on the right and the left draw upon our darker angels, scapegoating immigrants and Muslims or bankers and business people," Romney declared at Trine University in Angola, Indiana.

Obama, speaking at Rutgers University in New Jersey, warned that some politicians don't care about what's true: "When our leaders express a disdain for facts, when theyre not held accountable for repeating falsehoods, and just making stuff up while actual experts are dismissed as elitist, then we've got a problem. The rejection of facts, the rejection of reason and science, that is the path to decline."

Obama then mocked Trump's proposal to build a wall on the U.S.-Mexico border: "The world is more interconnected than ever before. Building a wall wont change that."