Yes, I believe the death penalty is completely justified. If a person is a cold-hearted serial killer, why should we let them go on living? Some people are just plain evil and if they've committed a serious enough crime, such as the brutal murder of a child, then absolutely they should be put to death. They don't deserve to still be breathing our oxygen and we certainly shouldn't be spending money to keep them alive, even if it is in jail.
As the president of the United States of America, and as a person in general, he has every right to meet with a person to try to convince them what they believe in. Obama believes Clinton is the better candidate and that Sanders should support her. It is in Sander's best interest to listen to the president and probably follow his advice.
Bernie Sanders made unprecedented progress with young voters. He got more people to register than in any election before. His followers can help the Democrats win by a landslide in the fall. However, Obama and the Democratic party will have to honor what Bernie stands for to win his followers. They won't switch allegiance just because someone tells them to.
One thing that Barack knows how to play is politics. He also has experience in getting people to drop out of political races. He will simply state his case that now is the time to rally behind Hillary Clinton and help her get elected president in the upcoming fall election.