"The Lebanese Armed Forces cannot effectively police Sunni extremism!"

... so, which 'Army' could? HEAVILY Loaded question!  

"...While Sunni extremism in Lebanon is a multifaceted issue, the country’s current political vacuum has allowed it to grow. Lebanon has been without a government since the resignation of Prime Minister Najib Mikati in March over a dispute with Hezbollah. This inability to form a government acceptable to all parties, a common theme in Beirut, has a direct impact on Lebanon’s security situation. Without the guidance of a cross-sectarian executive branch, the country’s main guarantor of security, the Lebanese Armed Forces (LAF), cannot effectively police Sunni extremism and other violent symptoms of the Syrian civil war. Thus, it seems that the Lebanese state will be unable to deal with the growth of violent Salafism and the exacerbation of Sunni-Shia tensions.  "