It's no surprise that Coriolanus and Sejanus have been asked to go to the hanging. As Capitol kids, they have a leg up on the other recruits when it comes to Peacekeeper training. So even if they don’t have to do anything, they already look powerful and intimidating, since they’ve been encouraged to look that way since they were small kids. The fact that Coriolanus blames the district people for being poor speaks to how successful the Capitol has been at blaming the districts’ poverty on the districts. Sejanus is right: the district people are poor because the Capitol rations their food, not because they’ve done anything wrong.