I really liked your question, because I have often thought about the same thing. On the surface it seems that many biblical scholoars try to seperate the God of the OT and the God of the NT.
We need to find some NT bible references tthat support Imprecatory prayers we find in pslams.
We can start looking at some of the writings of Paul:
I Corinthians 16:22 (NASB) If anyone does not love the Lord, let him be accursed.
Galations 5:12 (NASB) Would that those who are troubling you would even mutilate themselves.
Then the words of Jesus himself.
Matthew 23:13-36 (NASB)
"But woe to you, scribes and Pharisees, hypocrites, because you shut off the kingdom of heaven from people; for you do not enter in yourselves, nor do you allow those who are entering to go in.
Matt 23:14 ["Woe to you, scribes and Pharisees, hypocrites, because you devour widows' houses, and for a pretense you make long prayers; therefore you will receive greater condemnation.]
Matt 23:15 "Woe to you, scribes and Pharisees, hypocrites, because you travel around on sea and land to make one proselyte; and when he becomes one, you make him twice as much a son of hell as yourselves.
Matt 23:16 "Woe to you, blind guides, who say, 'Whoever swears by the temple, that is nothing; but whoever swears by the gold of the temple is obligated.'
Matt 23:17 "You fools and blind men! Which is more important, the gold or the temple that sanctified the gold?
Matt 23:18 "And, 'Whoever swears by the altar, that is nothing, but whoever swears by the offering on it, he is obligated.'
Matt 23:19 "You blind men, which is more important, the offering, or the altar that sanctifies the offering?
Matt 23:20 "Therefore, whoever swears by the altar, swears both by the altar and by everything on it.
Matt 23:21 "And whoever swears by the temple, swears both by the temple and by Him who dwells within it.
Matt 23:22 "And whoever swears by heaven, swears both by the throne of God and by Him who sits upon it.
Matt 23:23 "Woe to you, scribes and Pharisees, hypocrites! For you tithe mint and dill and cummin, and have neglected the weightier provisions of the law: justice and mercy and faithfulness; but these are the things you should have done without neglecting the others.
Matt 23:24 "You blind guides, who strain out a gnat and swallow a camel!
Matt 23:25 "Woe to you, scribes and Pharisees, hypocrites! For you clean the outside of the cup and of the dish, but inside they are full of robbery and self-indulgence.
Matt 23:26 "You blind Pharisee, first clean the inside of the cup and of the dish, so that the outside of it may become clean also.
Matt 23:27 "Woe to you, scribes and Pharisees, hypocrites! For you are like whitewashed tombs which on the outside appear beautiful, but inside they are full of dead men's bones and all uncleanness.
Matt 23:28 "So you, too, outwardly appear righteous to men, but inwardly you are full of hypocrisy and lawlessness.
Matt 23:29 "Woe to you, scribes and Pharisees, hypocrites! For you build the tombs of the prophets and adorn the monuments of the righteous,
Matt 23:30 and say, 'If we had been living in the days of our fathers, we would not have been partners with them in shedding the blood of the prophets.'
Matt 23:31 "So you testify against yourselves, that you are sons of those who murdered the prophets.
Matt 23:32 "Fill up, then, the measure of the guilt of your fathers.
Matt 23:33 "You serpents, you brood of vipers, how will you escape the sentence of hell?
Matt 23:34 "Therefore, behold, I am sending you prophets and wise men and scribes; some of them you will kill and crucify, and some of them you will scourge in your synagogues, and persecute from city to city,
Matt 23:35 so that upon you may fall the guilt of all the righteous blood shed on earth, from the blood of righteous Abel to the blood of Zechariah, the son of Berechiah, whom you murdered between the temple and the altar.
Matt 23:36 "Truly I say to you, all these things will come upon this generation.
God never changes.
