I just go by what Jesus said. I don't recall him making a point that one sin was worse than another. I am not declaring any sin to be worse than another. Sin is sin. If you know of somehwere where it says that please let me know.
The Old Testament is still part of the Holy Bible. Because Christ came and fulfilled the Law, it does not eliminate the truths found in its pages. It is clear from the Law of Moses and its punishments, which came from God, that some sins are more serious than others. That is an unchanging truth.