good people resist grace

When he (Paul) spoke of the Gentiles being 'without excuse' (Romans 1:20), there was no dialogue with them; they were silent, as if acknowledging the justice of their condemnation. It is the moral man, not the corrupt Gentile, who is disposed to argue, and to resist the unsparing and unqualified judgment that he is in the same predicament as the other, and in the same need of the grace of the gospel. 

It is significant, too, that this form of argument continues right to the end of the section, at Romans 3:20. The respectable, moral or religious man is much more difficult to convince of his need of grace than the other, and it is long before Paul an arrive at his verdict that 'the whole world' (including the good pagan and the religious Jew as well as the corrupt Gentile) is 'accountable to God' and guilty in His sight (3:19). (p35 Power of God: Exposition of Paul's Letter to the Romans)