They could have said that, but ultimately it would have been a mistake, I think. Mostly because of things that have been alleged about the incident, their safety record, and the fact that the average number of barrels spilled by thousands of other Gulf platforms (including numerous deepwater wells) was on the order of 1000 barrels yearly.
No one would have felt small-minded to focus on those details, especially as the total number of barrels climbs toward 5 million.
Bottom line, you need to be near the top of the hill to take the moral high ground, and by all accounts, BP was near the bottom.