I think they where worried (rightly so) that if they did not address the issue it would come to really bite them in the ass later and likely assumed they would not be the only ones getting the tainted lettuce to come forward. Instead they did the very least they could do (stop selling the lettuce and warn people), and now they are known as a key source to the mess.

I think the thing that gets me though is unlike the Spanish flu there is a clear villain in the story, Taylor Farms. Somehow I doubt the real name behind the shits will never really get in a proper level of shit.