@Duckiedoggo
Look at it for Yukine’s point-of-view.
First of all, Yukine only know about the whole Ebisu thing secondhand because Yato used Nora during the trip to the underworld. The gods are also hiding a lot of details because they can’t tell their vessels about “the gods’ greatest secret”.
So everything bad that Yukine knows about father is secondhand. Now, Yato suddenly just left with no explanation. This the second time Yato left Yukine to fight using a different vessel. Yato wants to keep Yukine safe, but he doesn’t explain this to Yukine, so Yukine feels that Yato doesn’t trust him. Combined with his memories of abandonment returning, Yukine can’t trust Yato anymore, including what Yato tells him about Father.
This is on top of his corruption from finding out “the gods’ greatest secret”. Remember, most vessels that remember their past went mad and turn into demons and attack everything around them. The fact the Yukine can still keep his human form and can focus his attacks instead of just killing everyone he sees shows that his mental strength is actually pretty amazing.