That's going a bit far. They do in fact fund and encourage movments such as hezbollah, that act as proxies for their agenda. I don't think those groups are a significant threat to the U.S., but they are a threat to Israel and Lebanon, in their way. And they can be a threat to the U.S., when they want to be, such as when they sponsored the massive attack on the U.S. Marine compound in Beirut.
Just saying, they ain't saints, and their capability to cause harm deserves respect. Which doesn't mean we have to bomb Iran because of hezbollah, but you shouldn't put the Iranian regime on some virtuous pedestal. There are no good guys.
Except for maybe the Swiss.