Obviously, but what does that comment have to do with anything? So corexit is harmful. My gp was talking about nuclear explosions and bacteria, not corexit.
The grandparent also said, "so it wasn't quite as big of an environmental disaster as first expected." The comment about corexit would appear to refer to that part.
You could argue that it was or wasn't as big of a disaster as expected, but the corexit comment was certainly relevant regardless.