Anger is not sin. Jesus was angry --and was without sin:
Hebrews 4:15 For we have not an high priest which cannot be touched with the feeling of our infirmities; but was in all points tempted like as we are, YET WITHOUT SIN".
Anger only becomes a sin if we choose to transgress the law of God:
1 John 3:4 Whosoever committeth sin transgresseth also the law: for sin is the transgression of the law.
The Seven Deadly Deceptions Of Counterfeit Christianity