If any one saith, that all works done before Justification, in whatsoever way they be done, are truly sins, or merit the hatred of God; or that the more earnestly one strives to dispose himself for grace, the more grievously he sins: let him be anathema.
It's not a universal opinion amongst them, thankfully, but this opinion may be found among the Reformed even today. It is a perverse theology that "justifies" the claim that the atheist who rushes into a burning building and saves another's life has not done something good.
No doubt they hold this view because they think that if a man can do good, then he might be able to live a completely righteous life without grace, or that he might be able to merit justification by virtue of such actions. This view is false. Man's end—the Beatific Vision—is beyond his powers to attain even if he were not hindered by sin (which he is). Consequently we are completely dependent upon grace in order to attain that end. Hence there remains no good grounds for pretending that the unbeliever is unable to do any good at all.