I don't know that theft is a moral reason for anything. I'm also not sure about your definition of "needlessly dying" or the nuances of how you get from forcibly taking people's stuff to achieving the goal of preventing "needless death."
I would actually argue the exact opposite (I also wouldn't use that as a reason to not-pay taxes since he was talking about Rome).
You're undoubtedly talking about this instance:
Luke
20:25 So he said to them, “Then give to Caesar the things that are Caesar’s, and to God the things that are God’s."
People normally think that because the coin has Caesar's image on it, then Jesus is saying (1) it belongs to Caesar and (2) so you should give it back to him when required. But I think that misses what's happening. Jesus pointing out the image on the coin with the inscription “Caesar Augustus Tiberius, son of the Divine Augustus” would have pointed out that Jesus' opponents were committing idolatry by having this image of a so-called god in the temple - the house of their God. According to Josephus, Pharisees had committed acts of treason against Rome for similar things in the past, such as tearing down the Roman eagle (eg. War 33). Jesus' move in pointing out the image on the coin was to make his opponents (the scribes and priests who should have known better) look like fools and win the opinion of the crowd.
Any Law-aware Jew listening to Jesus say, "give to God the things that are God's," probably wouldn't have missed the point when he recalled this from the Law:
Deut
10:14 The heavens – indeed the highest heavens – belong to the Lord your God, as does the earth and everything in it.
Or the various Psalms and other writings that recall this law, such as:
Psalm
24:1 The Lord owns the earth and all it contains,
the world and all who live in it.
So, assuming we look at Jesus is his historical context of 1st century Judaism, and he believes that everything on earth belongs to God........then what belongs to Caesar? Obviously -
nothing. His audience would doubtlessly have understood it that way, and in fact we have direct evidence that's exactly what they heard:
Luke
23:2 They began to accuse him, saying, “We found this man subverting our nation, forbidding us to pay the tribute tax to Caesar..
So I would argue that Jesus told them not to pay the tribute tax to Caesar. His opponents thought they could trap him by forcing him to say to pay the tribute tax to Caesar, since going against the tax would have been sedition against Rome and punishable by death. But if Jesus had given into Caesar's tax, he would have lost the crowd, as the Jews of the 1st century hated Roman rule and the tribute taxes they imposed on the Jewish people. Jesus not only didn't fall for it, he instead upped the ante by making the scribes and priests out to be idolaters, and won the favor of the crowd by encouraging sedition against Rome by advocating against paying the tribute tax. The crowd would probably have loved the message.
Luke
20:26 Thus they were unable in the presence of the people to trap him with his own words. And stunned by his answer, they fell silent.
Of course they were stunned - Jesus was confronting both Jewish and Roman authority and the crowd was on his side.