Hi Andrew 1992,
Is it a sin to Hate ? Yes of course it is - because the act of hating closes the heart to feelings of generosity towards the person/ object of hate. In so doing, the heart is denying love towards that entity, and replacing it with anger and bitterness, which starts to grow like a mould and then a cancer, gradually eating away at your spiritual being (soul).
Hate can become a habit that replaces love in our daily lives, and the human condition encourages it, through aggression, competitiveness and the survival of the fittest - it can spread across our psyche, shutting out the light of truth and love, creating shadows and darkness through fear and oppression.
This is the very reason why Jesus came among us, to demonstrate the ‘Living Word of God’, and to show us how to overcome this fundamental human problem - the one commandment - to ‘Love your neighbour as yourself’ (your enemies are your neighbours too).
Confession/Reconciliation comes in now - to clear up the mould and darkness in our soul before the cancer sets in lest it dies. Compare how often we take a shower or bath with how often we cleanse ourselves spiritually through reconciliation. In the existence of our human condition, we can’t help getting dirty, or committing sin from time to time - but we need to stay healthy in both cases, so no more hate !!
God bless