I do not have to prove anything. I agree to some things from the Vedas, accept some without really agreeing with them, do not accept some other things. For me, it is not the 'word of God' or the sole scripture of my belief. It was their time, their society, they did what they believed in. Then we merged with Hindus, took up some of their ways while retaining our ways. Where is the problem?
1. People pray to preserve and increase what they have, although it is debatable if that helps in any way. 2. Their ways. All aboriginal societies had sacrifices, many still have. What is 'qurbani'? 3. They were herders and everyone prepared ghee. I do not know if they knew of vegetable oils. 4. Horses are useful in steppes to round up cattle and also in skirmishes. 5. If not horses, which animal they should have used in chariots, asses? 6. Sure, all societies have to look after their safety. This obligation in Aryan society was given to 'kshatriyas'. 7, 8. All armies go to war under a leader. 9. Except for one in the late Vedic period (Battle of Ten Kings), there is no mention of a big war in Vedas. They were local, village level conflicts. 10. No, basically, it was to safe-guard what they had. Aryans were not like mongol hordes.