I think I’ve worked out why (apart from the obvious world peace and so on) Jesus told us not to hate our enemies, but to love them and pray for them.
If you hate your enemies, you will become like them. And then one day you’ll realise you hate yourself.
If your love your enemies, and pray for them, they might just become like your friends and love you back. Or if not, your still in front because you will still find it possible to love yourself and hopefully you will have spent a fair bit of time talking to God. Simple, isn’t it.