‘Can ye be angry and sin not? (Author’s translation). Let not the sun go down upon your wrath: neither give place to the devil’ (Eph. 4:26,27).
-Charles Welch (Things Most Surely Believed)
The anger is to be transitory. The quotation is from Psalms 4:4 (Septuagint), where Hebrew reads, "tremble, and sin not", the meaning of which is shown by the use here, for it is as easy to tremble from anger as from other powerful emotions.
-E.W. Bullinger (Companion Bible Notes)
Uncontrolled anger is a terrible thing. It often originates from the old nature (flesh). And even if we lean towards Bullinger's commentary, "righteous indignation" is often mixed with carnal hatred. We need to be very careful with anger.
I believe that Judas was a believer and has resurrection life. However, he lost all (perdition) reward and blessings because of his greed and anger. Take note the circumstance of his decision to betray his Lord.
When the Lord was at the home of Simon the Leper in Bethany (Matt 26; Mark 14; John 12), he was chastised by the disciples for allowing a woman to anoint him with expensive oils. It was after this upbraiding that Judas sought for an opportunity to betray him.
"For it might have been sold for more than three hundred pence, and have been given to the poor. And they murmured against her."
"And Judas Iscariot, one of the twelve, went unto the chief priests, to betray him unto them."
In John's account, he singles out Judas' anger:
"But one of His disciples, Judas Iscariot, Simon’s son, who would betray Him, said, 'Why was this fragrant oil not sold for three hundred denarii and given to the poor?'"
Judas' greed was couched in concern for the poor. His anger then led him to betray his Lord and master.
I'm not saying there are not times where "righteous indignation" may have a place, I am only saying that the emotion of "anger" is a dangerous thing. And how often has "self-righteousness" or "self-aggrandizement" (look at how much I care!) been hidden under the mask of "righteous indignation?"
I think it is good to start with the translation option of "can ye be angry and sin not?" before we chalk up our anger as "righteous indignation." We need to ask ourselves if we have that capacity. Are we truly concerned or are we simply filled with either rage or self-importance?