Since long before he was a politician, he’s lied frequently and even written in multiple books about his profound belief in the value of lying as a means to get ahead. And he’s good at it. After his Atlantic City casinos went bust, he successfully duped a bunch of mom-and-pop equity investors out of their money to get out of debt and had them pay him a salary for the privilege. He then got himself elected president and immediately started bullshitting about everything from the size of his inaugural crowds to the way NATO works to Chinese currency manipulation.When someone has proven over and over again that they are not trustworthy, you can, and in important situations should, stop trusting them
Matt Yglesias is right here but the bigger point is that they have shown themselves willing to make this exact kind of lie, as so has the Republican party. The GOP has made it clear they are OK with abusing national security for partisan politics when they lied us into a disastrous Iraq war. They outed Valerie Plame. They lied about the Iran treaty. They pardoned everyone involved in Iran Contra. It just keeps happening.
You can’t trust Trump not to abuse national security for partisan gain because you can not trust the Republican party not to abuse national security for partisan gain.