This means that we should not attack and destroy evil because we would not be able to differentiate between those who are evil and those who are good.
And many Fundamentalist Christians do exactly this.
Especially those who practise Spiritual Warfare.
They attack Hippies and Gays because they are left-wing and liberal and they support right-wing racism and prejudice.
They also support the rich.
So Jesus was quite right to tell his disciples not to uproot evil because they would not have seen clearly enough to do so.
"'You hypocrites, first take the log out of your own eye, and then you will see clearly to take the speck out of your neighbor's eye.'" Matthew 7:5 (NRSV)
[Scripture quotations (marked NRSV) are taken from the New Revised Standard Version Bible, copyright © 1989 by the Division of Christian Education of the National Council of the Churches of Christ in the U.S.A., and are used by permission. All rights reserved.]
Photo Credit: lena_lozhkina Flickr via Compfight cc