An intelligent and accurate assessment. May I repeat it?
1. For whatever reason that the rig blew, BP correctly owns the ultimate responsibility.
2. For whatever reason, the federal government abjectly failed to respond to its sole responsibility, by law, for mitigation.
3. Further, the Obama administration and the Democrat Congress are solely to blame for BP having to drill in those difficult circumstances.
At bottom, that's the only way blame can be assigned.
Actually, Transocean owns a piece, too -- it eventuated that their rig crew made some unauthorized field modifications to the controls of their blowout preventer stack and kill lines. They were not, as they say in the industry, "100% API" (American Petroleum Institute, i.e. "standard").
Halliburton may also own a sliver for selling BP a "magic" new cement formula which may have failed under testing conditions in the "Macondo" well.