Your stance is that loving good or hating evil implies we are able to differentiate between the two, which is a stance of moral superiority. Jesus did not say we should never use judgment (discernment), he said don't judge others (i.e. don't be judgmental or a hypocrite). In fact, he commands us to fix our own faults first, which implies knowing the difference between good and evil, so we can see clearly enough to help our brothers.

I think the hang up is the way Aquinas phrased the last sentence "you are immoral as well as unjust." He is not condemning the reader, he is merely saying that it's a natural response of people with morals to get angry when they see injustice. It's more of an approval to have righteous indignation.

Your original statement that "Christians should not judge," must be placed in the correct context. Jesus says (summarizing) "don't be a hypocrite. You will be judged by the same measure you judge others. Instead, correct your own faults, and then you might see clearly enough to help your brother." Being able to correct your own faults means we have the ability to judge between good and evil, and align with it (i.e. love it or hate it).

When you say "Loving good and hating evil implies being in a position to do so" you are saying we shouldn't make a judgment on good or evil because doing so implies we are morally superior. First, this is not the same "judging" Jesus was talking about and in fact he did command us to discern between the two. Second, what you are describing is moral relativism, which is a completely worldly ideology. Christians do not believe in moral relativism, so you cannot bind them to its tenets.

Your original statement that "Christians should not judge," must be placed in the correct context. Jesus says (summarizing) "don't be a hypocrite. You will be judged by the same measure you judge others. Instead, correct your own faults, and then you might see clearly enough to help your brother." Being able to correct your own faults means we have the ability to judge between good and evil, and align with it (i.e. love it or hate it).

When you say "Loving good and hating evil implies being in a position to do so" you are saying we shouldn't make a judgment on good or evil because doing so implies we are morally superior. First, this is not the same "judging" Jesus was talking about and in fact he did command us to discern between the two. Second, what you are describing is moral relativism, which is a completely worldly ideology. Christians do not believe this, therefore you cannot hold them accountable to a worldly misunderstanding.