Here Dr. Erich Bloodaxe RN does a good job of explaining why Ron Paul is an illiberal menace. So yeah by all means loathe Paul. But if you're a committed progressive, you have no choice but to loathe some of President Obama's actions related to war, imperialism, and civil liberties. Paul's opposition to some of these immoral, dangerous, and in some cases racist polices is the only reason why progressives give a hoot about him.
President Obama's record in this area is not all bad. For example, he signed executive orders banning torture, closing CIA secret prisons, and pledging to close Gitmo (I know but) within a year. And he's done some good things on nuclear disarmament. But overall, he's entrenched Bush's War of Terror and the overall militarism that passes for a foreign policy.
Some examples:
He's tripled the size of the force in Afghanistan, escalating a doomed immoral war.
And massively increased drone attacks, killing many innocent people, including children.
Intensified our dirty wars in Pakistan, Yemen, and Somalia.
Used cluster bombs in Yemen, killing innocent people, including children.
Tried to gut the ban on cluster bombs.
Codified indefinite detention.
Denied prisoners at Bagram basic rights.
Waged a war on whistleblowers.
Waged a not-so-covert war against Iran.
If the Greenwald-bashing were coming from people who'd spent a lot of time speaking out against the above policies, I'd take it seriously.