Should Christianity deny the fact that the Bible contains stories that promote genocide and ethnic cleansing and the mass murder of men women children and babies?
In order to answer this question you have to be more specific. God ordered men women and children to be killed on certain occasions. The reason was for abominations committed. The people in question were committing child sacrifices to demons. The Jews disobeyed this command every time thinking they knew better than God what to do. Less than two generations later the Jews had adopted these practices and were sacrificing their children to the demons, Moloch, Baal, and Ashera. You cannot look backwards into time and try to project your thoughts or even your terminology on the era in question. You must understand the time as it was back then. Child sacrifice is abomination to God and deserving of death. Read the Bible and understand it in context, not in any political or ideological agenda you may have and it will make sense. God gave the Jews 900 years to correct their ways before he wreaked havoc on them. Read Ezekiel where God chronicles all of their misdeeds you are asking about. God gives a list of the things the Jews had done and the people that taught the Jews to do these things throughout time. So if by genocide you mean God ordering the death of people that murdered babies yes there is genocide in the Bible. Ethnic cleansing NO. They were killed for what they did not who they were. Jews were ordered by God to be a light to the gentiles but the Jews didn't understand this. They thought they were better than the gentiles. God has since proved them wrong.
That is not always the reason. God ordered Israel to take the land of the Philistines and He ordered much slaughter - just in wartime. That had nothing to do with sacrifices to demons.