Tempest is the media's latest obsession and, frankly, that pisses Nico off. It's not that he doesn't like the guy — he just wishes everyone would shut up about him. But Nico is falling in love with him, and he doesn't even realize it.
And of all the times Jason could possibly start falling in love with someone, the absolute worst, most inconvenient, least expected, and completely unforgivable time to do so is now. Unfortunately, now is when it happens.