It's simply true that most Americans don't understanding how many different ways social networking happens in other countries. Even if a group of people has not intentions of committing acts of terrorism, they ways in which they keep in contact, both legal and extra-legal, can be used as avenues for terrorists to infiltrate the United States.
Yes, Koch drawing parallels between Trump and Hitler is going a bit too far. While Hitler's rise and ultimate brutality is a cautionary tale for any world leader, the parallel fails because Jews were not engaged in a worldwide battle against infidels to their religion. Trump's Muslim ban may be a regulatory overreach, and some provisions have already been struck down in federal court, but at present, the Hitler comparisons are still just inflammatory remarks.
If someone doesn't like something that another person does, they just run to call them Adolf Hitler. It's so common anymore that it can't be taken seriously. These people just want to find a way to say terrible things about someone else, and it's not helping words in a nation already divided.
I mean, pretty much everything the Trump admin is doing can be likened to Hitler. It sounds hysterical, but I think that's because Hitler and Fascism have been bastardized as terms.
Conway/Trump/Bannon are attacking anyone who criticizes them.
Trump is pushing wildly unconstitutional EO's quickly.
He's gaslighting the US with claims of voter fraud (definitely to enact some "voter ID" laws that will basically be voter suppression).
He's pushing this "terrorist threat" fear-mongering and claiming that only he and the feds can fix it.