Actually, I wouldn't have known about the history without this painting being destroyed. Balefour is now in the public consciousness, more so than he was a week ago.
Because this dead guy is historically significant to the conflict, as his actions led to the present situation. Understanding history helps us shape the future.
Abusing a child is wrong. Feeling the urge to do so doesn't make someone evil, so long as they recognize it's wrong to do so. The best way to stop kids from being abused is to teach why it is wrong and help those with the urges to manage them. Calling people evil detracts from that goal.
Actually, I wouldn't have known about the history without this painting being destroyed. Balefour is now in the public consciousness, more so than he was a week ago.