The Set repented.
Fallen angels can repent.
Anyone with free will can repent.
Anyone who repents can be forgiven.
Love your enemies means teach the gospel.
Satan doesn't want you - or them - to know this.
Unsure? - Matthew 15:26-28
But he answered and said, It is not meet to take the children's bread, and to cast it to dogs.
And she said, Truth, Lord: yet the dogs eat of the crumbs which fall from their masters' table.
Then Jesus answered and said unto her, O woman, great is thy faith.
How Is it Done? - Mark 16:15
And he said unto them, Go ye into all the world, and preach the gospel to every creature.