Well let me give you a list, then, of what I believe many modern Christians are ashamed of:
1) Genesis and evolution contradict
2) Exterminations of men/women/children in the OT
3) Eternal torture in hell
4) Demons
5) Commands in the OT that give the death penalty for apparently trivial crimes (e.g., the execution of children for cursing parents - also endorsed by Christ)
That's just a short list: I believe there is much in Scripture that has been abandoned.
None of that is particularly difficult once three factors are understood:
1. Progressive revelation. Jesus exemplifies this in His discussion of divorce and the law, saying, essentially, "You weren't ready in Moses' day for My real requirements." The OT was for a Bronze Age people. God did not hold OT believers to the same standard as Jesus holds Christians today basically because the Holy Spirit did not operate as a constant Counselor for them as He is for Christians. The New Covenant is one of "better promises" from both parties, replacing a now-obsolete Old Coventant, God as well as His believers. Jesus does not repudiate the OT, but Jesus does give an enhanced set of commands to His followers that were not placed upon the OT Bronze Age believers.
2. Semi-understood implications by the OT writers as well as early believers. Not "misunderstood" or even "poorly understood," but not
fully understood in all their implicatioins and ramificaitions. The best examples are all the Messianic references of the OT that were still "semi-understood" even by the first century. But another example is "do not bind the mouths of the kine that tread the grain," which Paul tells us was never about oxen, but about full-time workers for the Lord.
3. There is a spiritual realm of spiritual beings. Believers gonna believe; unbelievers gonna unbelieve. Nothing to do about that but FIDO: File It and Drive On.
4. It was not the mission of Jesus to "fix" the Roman Empire. It was not His mission to make the Roman empire or any other earthly kingdom look like Heaven or run like Heaven. Christians are "aliens," "ambassadors," "pilgrims and sojourners" in the nations of the world...not natives and not a rebellious army. Therefore, earthly kings in this fallen world will continue to operate as earthly kings in a fallen world, and the Body of Christ will perform it's mission around them, not attempting to overturn them. Therefore, there are elements of life in ancient times that Jesus (and Paul) do not dwell on as "things to fix in the Roman Empire," but explain instead how Christians are to relate to one another within the the world in which they find themselves.
There is one big truth modern Christians shy from. Christian moral philosophy is at its base deontological. Yes, it is Divine Command theology: If God says it's right, then it's right in all its ramifications.
There are two "problems" to acknowledge in holding Divine Command as one's personal moral philosophy: 1) Being sure one is truly hearing from God; 2) Being sure one accurately understands God's command. But
all moral philosophies have their problems.
Within the Body of Christ, we may debate long and hard specific issues on those two points, but we should agree with the basic premise that
when we do know we are hearing truly from God and that we are
accurately interpreting His command, then that is a morally correct command for
us to obey.
Christians have to own up to Divine Command Theology. It's the very same philosophy of the Roman centurion who amazed Jesus by his faith.
Christians should also understand as evangelists that it is not necessary to completely demolish a prospective believer's current understanding of the world in order to present the gospel to him, or for him to accept it.
The Philippian jailer already believed in a full set of pagan creation myths and philosophies the night he slammed the doors on Paul and Silas. Paul and Silas did not need to convince the jailer of Genesis before he could accept the gospel. He accepted the gospel first and got the rest later. Those the Holy Spirit has made ready to accept the gospel will accept it "as is," and will defer their other questions until later.
I have a good friend who spent 12 years in Morocco as a pretty successful undercover missionary. His technique was simple. The Muslims he encountered observed him living a Christian life "in all Godliness and holiness." Those who were receptive to the Holy Spirit came quietly to
him with the plea, "Tell me about Jesus."
He did not try to demolish their Islamic beliefs, he did not hit them with theological doctrine. He merely sat with them and read the gospels, then Acts, then Romans, answering questions as they arose. Then he'd merely ask, "Do you believe what we've read?" He reports that any Muslim who stuck with him through at least Romans would respond, "Yes, I believe it. I want to be baptised." Those who weren't ready didn't stay that long.
The gospel is much slimmer than we often make it.