I'm not sure I get this.

2 Thessalonians 1:3-9(NKJV)

We are bound to thank God always for you, brethren, as it is fitting, because your faith grows exceedingly, and the love of every one of you all abounds toward each other, 

so that we ourselves boast of you among the churches of God for your patience and faith in all your persecutions and tribulations that you endure, 

which is manifest evidence of the righteous judgment of God, that you may be counted worthy of the kingdom of God, for which you also suffer; 

since it is a righteous thing with God to repay with tribulation those who trouble you, 

and to give you who are troubled rest with us when the Lord Jesus is revealed from heaven with His mighty angels, 

in flaming fire taking vengeance on those who do not know God, and on those who do not obey the gospel of our Lord Jesus Christ. 

These shall be punished with everlasting destruction from the presence of the Lord and from the glory of His power, 

Not sure what to think of this.  I think we have all heard the phrase "vengeance is mine sayeth the Lord".  This seems to go along those lines.  What I find interesting is that it says it is a righteous thing when God takes vengeance on our behalf.  That almost makes it seem that it is required that He take vengeance.

I'll have to keep an eye out for more Scripture supporting or negating the idea.