Hezbollah is one of Iran’s guerrilla armies. Domestic policing and security is insufficient to stop a foreign guerrilla army. They must be stopped on their home soil. They won’t stop, until they’re beaten to the point of having no more will to fight. Any nation or individual who supports Hezbollah is an enemy of the United States.
Of course we would have to respond violently if Hezbollah ever attacked us here in America, but we shouldn’t want to fight Iran and Hezbollah unless we have to as they’re useful in balancing against the terrorists who have been attacking the West the last 20 years.