Walter Russell Mead provides a good explanation about the Paradox:
Capitalism, the social engine without which neither Europe nor the U.S. would have the wealth or strength to embrace liberal values with any hope of success, is often seen as a cruel, anti-human system that is leading the world to a Malthusian climate catastrophe. Military strength, without which the liberal states would be overwhelmed, is regarded with suspicion in the U.S. and with abhorrence in much of Europe. Too many people in the West interpret pluralism and tolerance in ways that forbid or unrealistically constrain the active defense of these values against illiberal states like Russia or illiberal movements like radical Islam.