James 2 :10 How ties in with venial and mortal sin?

from here: http://www.calledtocommunion.com/2011/11/why-john-calvin-did-not-recognize-the-distinction-between-mortal-and-venial-sin/#comment-50856

The role of agape in fulfilling the law allows for a principled difference between violations of the law that are incompatible with agape and violations of the law that are compatible with agape. And that is precisely what differentiates mortal and venial sins, respectively. Because agape fulfills the law (Rom 13:8,10; Gal 5:14), there is a distinction between sins that go against agape, and sins that fall short of the perfect expression of agape but do not go against agape. In this way differences in the condition of the heart from which a disordered action comes, with respect to agape, allow for a principled difference between mortal and venial sins. But if one approaches the question of sin only from the point of view of the letter of the law, one cannot see the basis for any such distinction.

Calvin thinks that James 2:10 supports his position. “For whoever keeps the whole law and yet stumbles in one point, he has become guilty of all.” (James 2:10) He likewise takes “the soul that sins, it shall die” (Ez. 18:20) as supporting his position. But the Catholic understanding of these verses is that they are about mortal sin, and it would be question-begging to hang the justification for a schism on the assumption that there is no such thing as venial sin, and that St. Augustine et al were wrong about the existence of venial sin.

The passage in James would not make sense if it were not indirectly referring to some principle that underlies the law, namely, agape. How does a person who steals thereby violate all the other commands of the law? He does so by going against the agape that fulfills the whole law. And therefore the kind of violation of the law in view here in this verse is best understood as one that is contrary to agape. If we go ‘behind’ the law to see the role that agape is playing in the fulfillment of the law, then instead of making righteousness equivalent to fulfilling the letter, we can see righteousness as the fulfillment of the spirit, even when we fall short in the letter