Former U.S. President Barack Obama, left, delivers his speech at the 16th Annual Nelson Mandela Lecture at the Wanderers Stadium in Johannesburg, South Africa. Picture: AP Photo/Themba Hadebe

Johannesburg - Barack Obama finds it hard to believe that in 2018 it's still important to talk about how wrong being prejudiced against others was.

Speaking at The 16th Nelson Mandela Lecture at the Wanderers Stadium on Tuesday afternoon, the former president of the US said people's differences were only superficial and it was incredulous that that was something that people still needed to be told today due to their prejudiced nature.

He said one of the principles Mandela taught him was that "we're bound together by common humanity but I still have to stand here today and say out differences are superficial.

"It's amazing to still have to stand here and do that but it turns out that in reactionary politics, the struggle for social justice not truly finished," he said.

Obama said people needed to guard against those trying to elevate themselves at the expense of others. He also said when it comes to fighting for the rights of others, such as gay rights, people should not say "those are just Western ideas."

Praising Mandela, Obama said the late statesman was so popular that he could have been a president for life if he so wished.

However, he instead helped draft a new constitution that also states presidential terms.

The Star