Jesus often speaks in terms of polarities, his right hand and his left hand, the last first and the first last, but he does not believe that real life exists only in such categories.  We are the trees that he speaks of at the beginning of today's gospel reading, and we produce both good AND bad fruits.  And Jesus does not expect anything different.

What he does expect is that if we wish to listen to him and to follow him we will seek to eliminate the evil in our actions, in our desires, in our attitudes.  It is this desire to be completely his, and not the purity itself, which is the fruit of his grace within us and the only fruit that counts --- as long as it is a real desire, one which we truly try to realize even at some cost to our selves and to our comfort.