There shouldn't be any questions about whether the Pirates should be buyers or sellers at the deadline this year. They're 38-42, 5.5 games back in the Wild Card race, and have five teams between them and the two Wild Card spots.
There also shouldn't be any complaints if they decide to rebuild. At best, the Pirates were looking at a Wild Card appearance this year. They need to aim higher, and the best way to aim higher in today's MLB is to go all-in as either a buyer or a seller. This isn't a team where you go all-in and add to the group.