Is it wrong to be mad?

It's not wrong...everyone gets mad! But if you find it happening a lot (i went through this lately), try praying and ask God to not let these people get under your skin. Instead, look at them with compassion and pity, they know not what they do.

Remember Christs attitude. When speaking to those who used God to fulfull their own lusts, He was angry, but when He Himself was fully mistreated, spat upon. slapped, taunted, flogged, beaten, and crucified, He remained humble.
Read this:

Ephesians 4:

25 Therefore each of you must put off falsehood and speak
truthfully to his neighbor, for we are all members of one body.

26 "In your anger do not sin": Do not let the sun go down while you are still angry,

27 and do not give the devil a foothold.

28 He who has been stealing must steal no longer, but must work, doing something useful with his own hands, that he may have something to share with those in need.

29 Do not let any unwholesome talk come out of your mouths, but only what is helpful for building others up according to their needs, that it may benefit those who listen.

30 And do not grieve the Holy Spirit of God, with whom you were sealed for the day of redemption.

31 Get rid of all bitterness, rage and anger, brawling and slander, along with every form of malice.

32 Be kind and compassionate to one another, forgiving each other, just as in Christ God forgave you.

Being mad is a safe stage on a fine line. Being mad or angry about something is normal, not okay (Ephesians 6:24-32) as long as you do not let it turn into a grudge or bitterness. Basically, we as human flesh are going to get angry about things because we do not understand. Though we fail to realize that it DOES NOT matter if we understand. We must do as David did in Psalms 28:7, " The Lord is my strength and my shield; my heart trusts in Him, and I am helped. My heart leaps for joy and I will give thanks to Him in song." So trust in the Lord, and just let your anger go as soon as you realize it. You'll be just fine ;O)

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don't let your anger get into you, that's why we've to learn to be humble and wise like Jesus.
being mad's a human thing but don't stay mad forever

ask God to help you in your daily interaciton with people.

As Jesus said "If someone hits you on the one cheek, offer him the other."
But when someone is disgracing God, anger is perfectly in place.
Do not carry that anger like a badge though. Do carry your love of God and your neighbor as your badge.

I am mad, sometimes, too but later on, I always remember to forgive. And in turn, asks God to forgive me for the anger that I had sown within me.
Forgive your debtors, and God will forgive you, too.