Forrest received blame for things he could not control, and understood that we are often expected to make excuses even when we are not at fault. Processes that have only common cause variation can only be improved by changing the process. Too often, management blames employees for poor performance when the work process is producing within its normal capability. Further, management's attempt to assign blame to a specific cause will be fruitless, due to the random interaction of different causes. This unfair assignment of blame breeds distrust in the workplace.
People say the Earth is round.
But you don't have to believe it if you don't want to. Forrest was astute to notice that we don't have to believe in something just because it is the conventional wisdom. Experience alone is not the best teacher. Experience taught our ancestors that the Earth was flat. We need knowledge to predict the future.