i suggest you investigate the side effects of corexit that have emerged since the incident
these guys http://cat.inist.fr/?aModele=afficheN&cpsidt=24108904 suggest that it doesn't help the bacteria work, but doesn't suggest any enhanced toxicity.
There are plenty of links to reliable sources there. Which page were you looking at?
You could argue that it was or wasn't as big of a disaster as expected, but the corexit comment was certainly relevant regardless.
Damage from corexit would have be factored into initial concerns.