NEW : He calls former slave trade post a powerful reminder to keep focus on human rights . The United States has been accused of using the site as a way for people smugglers and traffickers to move slaves from Africa into Europe. He 's pushing U.S. investment , addressing development issues , promoting democracy in Africa . Nelson Mandela 's legacy will linger `` throughout the ages , '' Obama says .
NEW : He calls former slave trade post a powerful reminder to keep focus on human rights . Obama calls for decriminalizing homosexuality ; Senegalese President Sall says no . He 's pushing U.S. investment , addressing development issues , promoting democracy in Africa . Nelson Mandela 's legacy will linger `` throughout the ages , '' Obama says .