As I wrote on Friday, Senators John McCain and Lindsey Graham didn’t do themselves any good this week when they angrily trashed Senator Rand Paul’s 13-hour filibuster about drone attacks on the Senate floor. Sounding like angry old men telling the kids to get off their lawn isn’t the best way to respond to an event that galvanized the country and inspired admiration from both the right and the left. But rather than turn down the heat, McCain doubled down on his critique when he subsequently referred to Paul, Senator Ted Cruz and fellow libertarian Rep. Justin Amash as “wacko birds” in an interview with the Huffington Post that was published subsequent to his Senate remarks.

It should be understood that the Arizonan firing from the hip in this manner is just McCain being McCain. He doesn’t pull his punches, and, as is well known among those who have worked with him in the Senate, his lack of tolerance for those politicians who don’t measure up to his standards or who just annoy him is legendary.

But at this point that remark will do McCain more harm than it will the targets of his wrath. It will be seen as yet another indication that McCain and others who agree with him just don’t understand why Paul’s filibuster struck a nerve with so many in his party’s grass roots and inspired the admiration of many on the other side of the aisle as well. The word “wacko” signifies a lack of seriousness and the idea that those who fit the description are out of the political mainstream. The problem is that McCain, Graham and others who oppose Paul’s foreign policy views don’t seem to grasp that what is happening now is not merely excrescence of a marginal movement but the beginning of a serious policy debate about what Republicans believe about foreign policy. And the sooner he, and others who don’t want the GOP to drift away from being the party that stands for a strong America on the international stage, stop dismissing their opponents and start engaging them on the issues the better off they and the country will be.

It bears repeating that Paul’s bold gesture in the filibuster inspired admiration because it was a rare example of a Washington figure standing up for the principle of constitutional government with courage and grace. That he did so at the expense of an Obama administration that is so often cavalier about not respecting the Constitution endeared him to many Republicans who are not part of his libertarian base.

But the notion that all this fuss was about the Constitution and the right of due process is a cover for Paul’s basic disagreement with the GOP’s long consensus about foreign and defense policy. Paul spent much of Wednesday speculating about the possibility that an unprincipled future American president could use a drone to kill his political opponents or to punish dissidents of the Jane Fonda variety. That fired the imagination of paranoids on both the right and the left who are always ready to believe Big Brother is about to haul them off to jail. But the cheers Paul received went beyond that limited set to those who are uncomfortable with more than just the theoretical possibility of a drone attack on an America in the United States. It’s important to understand that Paul’s issue is not so much with drones as it is with a policy of what he calls “perpetual war” against Islamist terrorism and the entire concept of a strong U.S. policy to protect our influence, allies and trade in the Middle East.

Instead of venting resentment at the way in which the filibuster rallied conservaties, responsible Republicans should think back on Paul’s foreign policy address given at the Heritage Foundation last month in which he detailed his desire to reboot American foreign policy. That speech received a lot less attention than the filibuster but it showed that his goal is not so much restraint of American power at home as it is in cutting back abroad. Though he calls himself a realist in the mode of the first President Bush or James Baker, his embrace of containment as a strategy would have serious consequences for any hope for stopping Iran’s drive for nuclear weapons or the fight against Islamist terrorism.

Paul’s ideas are not so much “wacko” as they are dangerous. Though they seek to exploit American weariness with the wars in Iraq and Afghanistan, they mistake that understandable emotion for a widespread desire to retreat from the world. Though Paul wisely avoids the sort of rhetoric that marked his father’s isolationist views which seems to treat terrorism as America’s just punishment for its sins, his policies are rooted in the same mindset. Most Americans support drone attacks and don’t wish to contain a nuclear Iran. If Republicans follow Rand Paul and become the party that wishes to stop fighting Islamists while Democrats continue to pose as the killers of Osama bin Laden, foreign and defense policy will become a permanent advantage for President Obama’s party in the future.

No one can blame Republicans for being excited about what Rand Paul did last week, but they won’t win in 2016 or any other year if they become a party whose foreign policy earns the admiration of left-wingers like Ron Wyden. Halting this trend will require more than name-calling. It will require those who oppose Paul’s ideas to make their case on the merits as well as exhibit the same sort of moxie that the libertarian displayed in his filibuster. It is no small irony that McCain and Graham passed on an opportunity to filibuster Chuck Hagel’s nomination as secretary of defense over his views about Iran and containment. They seemed more concerned at that time with not appearing to be as much of a “wacko” as Ted Cruz, who took no prisoners in his attacks on Hagel. If they, and those who agree with them, are to prevail in the coming years and save their party they’ll have to confront Paul’s ideas as well as match his courage.