The enemy of my enemy is my friend. ~ Chinese proverb
Sen. Joe Lieberman had urged the United States to fund the Syrian opposition. Al-Qaeda has also endorsed and is participating in the Syrian revolt.
Reasons: Al-Qaeda has always been a Sunni Muslim faction; the Assad regime comes from a Shi'ite tribe. Sen. Lieberman has always considered himself Israel's representative to Congress; overthrowing Assad would weaken the anti-Israel Hezbollah (a Shi'ite faction).
Israel is already backing an al-Qaeda terrorist faction in Iran because it serves their purpose. Whether the CIA is also funding them or Mossad agents were just pretending to be US spies is still unclear. Israel's Likud government has its own goals and they are not often in the best interests of the United States.
Assad is engaging in genocide against his own people, just as Gaddafi was doing in Libya. There are many good, legitimate reasons to act to end the wanton bloodshed. But giving money and weapons to al-Qaeda because it will help Israel with her Lebanon problem is not one of them.