@oristarA,
Original: we are less comfortable with ideologies that demonize whole populations,
justifying their abuse or outright destruction. Using 'justifying' (gerund form) makes clear that what follows the comma is an statement of what 'demonize' includes. If you wrote 'and justifying...' then the 'and' would be introducing something additional.
Consider:
I set light to John's house, killing him and his wife.
I set light to Johns house, and killed him and his wife.