>Ultimately, refusing to engage with outlets like Fox doesn’t punish them.

I respect Psaki and agree that Harris' appearance is a net win. However, there can be an argument that engaging with Fox News legitimizes them. 

It is really a tough call - Fox would better suit the public just disappearing altogether. While they are still around, however, it seems beneficial to combat them on their home turf, even if it means they get the ratings from it.