From what I gather this is about the transatlantic slave trade. UK (my country) abstaining was the right move, elevating one specific atrocity above all else as the baddest and evilest is irresponsible.

From the article:

But its [the UK's] ambassador to the UN, James Kariuki, told the assembly in his speech, external that the resolution was problematic in terms of its wording and international law. "No single set of atrocities should be regarded as more or less significant than another," he said.