The Quran

يا أَيُّهَا الَّذينَ آمَنوا لا تَتَوَلَّوا قَومًا غَضِبَ اللَّهُ عَلَيهِم قَد يَئِسوا مِنَ الآخِرَةِ كَما يَئِسَ الكُفّارُ مِن أَصحابِ القُبورِ

Muhammad Asad

O YOU who have attained to faith! Be not friends with people whom God has condemned!¹ They [who would befriend them] are indeed bereft of all hope of a life to come² - just as those deniers of the truth are bereft of all hope of [ever again seeing] those who are [now] in their graves.³

Cf. 58:14 and the corresponding note 25, which explains the reference to those "who would be friends with people whom God has condemned".
I.e., only people without any real belief in a life to come can remain "neutral" between right and wrong.
I.e., because they utterly reject the idea of resurrection.