The biblical sign of spiritual immaturity is malice and slander towards others in the body of Christ.
Colossians 3:8 (NASB)
[SUP]8 [/SUP] But now you also, put them all aside: anger, wrath, malice, slander, and abusive speech from your mouth.
1 Peter 2:1-2 (NASB)
[SUP]1 [/SUP] Therefore, putting aside all malice and all deceit and hypocrisy and envy and all slander,
[SUP]2 [/SUP] like newborn babies, long for the pure milk of the word, so that by it you may grow in respect to salvation,