I will prove from the Bible alone that both claims are false.
Refutation of the first claim
The claim that the Romans killed Jesus is not actually wrong. In fact, the Bible really does report that the Romans were the ones who crucified Jesus. But this is a classic half-truth and a half-truth is also a lie. Because if you look at the biblical account as a whole, it becomes clear that the Romans did not want to kill Jesus but to save him and that it was the Jews who forced the Romans to kill Jesus.
Here is the evidence:
Pilate knew that Jesus was innocent and wanted to free him. So the Romans did not want to kill Jesus.John 19:4 And then Pilate came out again and said to them, “See, I am bringing Him out to you so that you will know that I find no grounds at all for charges in His case.”
Luke 23:20 But Pilate, wanting to release Jesus, addressed them again, 21 but they (the Jews) kept on crying out, saying, “Crucify, crucify Him!”
Jesus himself says that Pilate, i.e. the Romans, do not bear the great sin of the murder of Jesus, but those who handed Jesus over to the Romans. And those who handed Jesus over to the Romans were the Jews, according to the Bible.John 19:11 Jesus answered Pilate, “You would have no authority over Me at all, if it had not been given to you from above; for this reason the one who handed Me over to you has the very great sin.”
John 19:7 The Jews answered him, “We have a law, and by that law He ought to die, because He made Himself out to be the Son of God!”
Pilate knew that killing an innocent man was wrong and would have consequences, so he washed himself clean of the guilt of the murder of Jesus and the Jews replied to Pilate: "His blood be on us and on our children" This is a Hebrew expression that can also be found in the Old Testament, it means: "We pay for his death". The Jews themselves freed the Romans from the guilt and took the guilt upon themselves. Yes, they themselves.Matthew 27:24 Now when Pilate saw that he was accomplishing nothing, but rather that a riot was starting, he took water and washed his hands in front of the crowd, saying, “I am innocent of this Man’s blood; you yourselves shall see.” 25 And the WHOLE people (Israel) replied, “His blood shall be on us and on our children!”
Acts 2:36 Therefore let the WHOLE house of Israel know for certain that God has made Him both Lord and Christ—this Jesus whom you crucified.”
Some of you are wondering how it can be that all Israel was in Jerusalem, the answer is that Jesus was crucified on Passover, a pilgrimage feast, which means that all the Jews from all over the world were in Jerusalem (Deut 16:16). So they all wanted to kill Jesus, according to the Bible.
Jesus said: "Forgive them for they do not know what they are doing." He was referring to the Romans, because they really did not know what they were doing, they were just carrying out the order of the Jews. The end of the verse proves that Jesus meant the Romans and not the Jews, because those who divided his garments among themselves were the Roman soldiers and not the Jews.Luke 23:34 But Jesus was saying, “Father, forgive them; for they do not know what they are doing.” And they cast lots, dividing His garments among themselves.
Matt 26:59 Now the chief priests and the entire (Jewish) Council kept trying to obtain false testimony against Jesus, so that they might put Him to death.
Matt 27:18 For he knew that it was because of envy that they (the Jews) had handed Him over.
Matt 26:59 and 27:18 make it clear that the Jews knew what they were doing, they knew Jesus was innocent, they deliberately sought false witnesses and the reason they wanted to kill him was envy.
The Apostle Paul confirms: The Jews murdered Jesus.1 Thess 2:14-16 ...the Jews, who murdered the Lord Jesus and the prophets and persecuted the church. They displease God and are the enemies of mankind; forbidding us to speak to the Gentiles that they may be saved; with the result that they always fill up the measure of their sins. But wrath has come upon them to the utmost.
Refutation of the second claim
Yes, it is true that the fact that Jesus was crucified brought salvation and blessing, but that does not mean that the crucifixion of Jesus was not sin and not wrong. On the contrary, it was sin and wrong.
Here is the evidence:
Jesus declares: "Yes, I will go and die as the prophets prophesied to bring salvation, but that does not mean that my murder is not a sin! Those who delivered me to the Romans will pay the price"Mark 14:21 The Son of man goes indeed as it is written concerning him, but woe to that man by whom the Son of man is delivered up; it were good for that man if he had not been born.
First question: What happened between Palm Sunday and the crucifixion? First the Jews celebrated Jesus as the Messiah, but then they all wanted to kill him. So what happened?
Answer: The reason why the Jews celebrated Jesus as the Messiah was because they thought he would free them from the Romans. But when they realized that Jesus was not going to do this, they rejected him. So the Jews did not really accept Jesus as the Messiah in their hearts on Palm Sunday, because they were not celebrating because they truly loved him, but because of self-interest.
Second question: Why does the Bible say "all Israel" or "the Jews" murdered Jesus if there were also Jews who followed Jesus?
Answer: Yes, it is true that there were Jews who really followed Jesus, but they were very few, so few that the Bible uses generalizing terms like "all Israel" and "the Jews" in a negative sense. I mean, if there was a nation of 100 people and 99 of them are bad and only 1 is good, then everyone would also criticize that nation in a generalized way.
Quote from Bishop Melito of Sardis (2nd century): "What evil have you done, O Israel? You have defiled the one who honored you. You prepared for him sharp nails and false witnesses and fetters and scourges and vinegar and gall and the sword and affliction as for a murderer. You have killed the Lord in the midst of Jerusalem! Hear it, all the families of the nations, and see: outrageous murder has taken place in the midst of Jerusalem, in the city of the law, of the Hebrews, of the prophets, in the city that was considered righteous! He who hung up the earth has been hung up; he who fixed the heavens has been fixed; he who fastened the universe has been fastened to the wood; God has been killed; the King of Israel has been slain by the hand of Israel. Oh, what an outrageous murder! Oh, what an outrageous crime!"