One of the key assumptions of non-interventionist libertarians (who rankle at the term "isolationist") is that through trade and economic integration we can woo our enemies and make a profit all at the same time. The only problem is that it is almost never true.
Seth Mandel points out that letting Russia into the World Trade Organization didn't make it less aggressive: "It's because the economic integration of Russia has done precisely the opposite of what it was expected to do in one crucial regard: the recent events in Ukraine and the West's unsteady response indicate Russia's increased leverage instead." That is because the West's business interests become invested (literally) in a new market (thereby weakening support for any kind of sanctions) and because the aggressor gets economic benefits at no costs.
The same is true in lessening sanctions on Iran. Does anyone -well, other than President Obama and Secretary of State John Kerry - think lifting sanctions on Iran, letting business flow in and enticing European countries to turn a profit in Tehran will make Iran more compliant? It sure hasn't so far.
And if we need any more examples, take China. The country's trade and interaction with the West has boomed during a time of uniquely aggressive behavior in Asia and during a time of increased domestic oppression. Once again, economic integration seems inversely related to improving the behavior of rogue regimes.
What does help is integrating emerging democracies into international trade (e.g. the free trade agreements with Colombia) that can help their economy and resist the pressure of neighboring bullies (e.g. Venezuela).
When do despotic regimes lower the level of aggression? If experience is any guide, despots respond to signs of strength, not signs of what they see as weakness. Iran briefly gave up its nuclear ambitions when the U.S. attacked Iraq, for example. The pressure can also be rhetorical (e.g. Ronald Reagan calling the Soviet Union the "evil empire") or take the form of support for free peoples (as we did successfully in Central America).
The isolationists have it backwards. They'd like to in effect reward totalitarians with economic goodies. Instead, we should be doing everything we can to pressure them diplomatically and economically as well as supporting rebels rhetorically and militarily. When and if they turn over a new leaf, we can consider more fully integrating them into the international economic system. Otherwise, as Lenin said, we are simply selling them the rope with which we will hang ourselves.