I don't know about you, but I get my oil from Russia and pay well fo it. That's, you know, market economy. Try securing that, Rambo.
Also, Qaddafi was one of the most reliable suppliers, as all experienced autocrats are - being reliable is a must in long-term geopolitics. The invasion might've shuffled the income statements of vested corporations but was hardly necessary to ensure Southern Europe gets its oil. If anything, they would need actual cash to buy it, as I don't see BP supplying it for free.
Not to mention that many Americans don't want to defund the military. It's not like Gunfighter is some outlier. Such Americans like their military strong, regardless the foreign situation. Even if Europe raised defense budgets, they wouldn't support defunding the military. Hard power is the source of American hegemony and no military expenditures are high enough when there are still enemies out there, they argue.