The swastika on the base of the sculpture used as the murder weapon is a standard Nazi swastika with the arms hooking to the right, as is the swastika imprinted on the scalp of Karl (the murder victim). The imprint on the scalp should have been a mirror image of a Nazi swastika, with the arms hooking to the left.
The slave trade was abolished in the UK in 1807 so that what Henry's father was doing would not just have been repugnant but illegal. Slavery itself was sadly not abolished until 1833 with compensation paid by the British government to slave owners.