Let me try to help you see this through what I consider to be a fairly new perspective to understanding sin and the death and resurrection of Jesus. When I say new, I don’t mean unorthodox. If it doesn’t help then I apologize in advance.
I have been giving some thought to the matter and I have read the catechism a couple times, on the section about sin starting at CC 1846. I am left with more questions then answers. I don’t understand what exactly sin is and why it made it necessary for God to be crucified.
I will not try right now to address the death of Jesus by crucifixion. I will do that later. For now, let’s just focus on sin. Your question is a very fundamental one, and a good one. Let’s start by assuming that we all have the freedom to choose one thing over another. I can choose to do this that or the other thing. In fact, we do at every moment of every day choose to do one thing over the other. We generally try to choose to do those things that make us into something more than we are now, something better than we are now.
Somehow we know, as you have already indicated, that murder is something that would make us into something worse than we are. An act of murder would be wrong. You seem to believe that there are other things that it would be wrong for us to do, but those things might be lesser “wrongs” than other things we might do. This is not far from the truth. Of course it doesn’t mean those other things are not wrong - they do not make us into someone better than we are now. But how do we decide which of those actions we take in everyday life are things that make us into good people or (for lack of a better term) into bad people?
We look to what God has disclosed to us. I think you would even admit that this is what you are searching for. Perhaps you should start looking at sin from the perspective of what is good for us - what makes us better people - and not so much from the perspective of how it might offend God.
Mortal sins like murder, etc is one thing but the lesser sins calling for the necessity of the crucifixion seems a strange concept to a new Christian like me. Help me figure this matter out.
Not so strange if we look at the death of Jesus from a certain viewpoint. The title of your post suggests that you believe Jesus had to die on the cross as if he didn’t have any choice. He was a man you know, which means he did have a choice. In fact, Scripture makes it apparant that he knew of his impending death yet chose that path anyway. Why did he choose this path? Maybe you are thinking that he knew if he didn’t the rest of us would continue to remain in a state of sin, that is, continue to make bad choices. That is true, but maybe not for the reason you think.
Jesus knew that he had lived a sinless life, a life where he had made all the right choices. And he knew the people around him saw this as well. Jesus knew he would die publicly having made all the right choices. But the most important thing he knew is that he would be resurrected from the dead and be eternally close to God as a result. He knew he would be an
example for all of the rest of us that if we too live as good people in this world by having faith in God and keeping his commandments we can hope for the same resurrection and closeness to God. Jesus willingly gave his life so that we could see this. The crucifixtion is not a matter of a blood-thirsty God who demanded a sacrifice for the sins of humanity committed throughout the ages.
God loves us and so does Jesus. Jesus freely gave his life as an example for us. If we have faith in God and follow his commandments, we too can hope for resurrection and eternal closeness to God.