It was Moses not Abraham. Which people did they kill and which towns did they destroy on the way to Cannan. Source/verse.

The knowledge of the Kingdom was TAKEN to the Gentiles, not GIVEN to them...

First off it was Moses that lead the people out of captivity. Now as to the killing of thousands. The Israelites were surrounded by a number of different tribes. These tribes were cultic pagans who worshiped false gods. This worship included homosexual rituals as described in Leviticus 18:22. Also there were many descendants of the Nephelium , who were the giant offspring of angels who came to earth and had children with the women of these tribes. God did not want the children of Israel to incorporate homosexual cutic rituals into their worship as it was done in a manner that made gods of the participants. The Lord God said He wanted no other gods before Him. Usually after a battle the Hebrew soldiers were given the spoils of the battle that included all the women whom had not lain with a man and the male children. The soldiers could marry these captive women, make concubines of them or make them slaves. This is what generally happened to the older male captives. Very often however the young prepubescent boys were made sex toys for the owner/master. The Lord God was very much against the practice of pederasty. This is also included in Leviticus 18:22. As for the Nephelium among the tribes the Lord God wanted to rid the earth of these giant non-earthly offspring. Therefore the Lord God used the Hebrew warriors to rid them from the earth. It is very important to understand the culture and what was going on back several thousands of years ago. The Lord God did not Indiscriminately "kill" people. There was definite reason and purpose for the wars and battles. Learn the truth before accusing what occurred and why.