Frank understands that Angus likely got a phone call from Eric, was scared, and got drunk. Suspecting that Eric would come to the house, Angus tried to lure Frank away to protect him. Angus does genuinely care about Frank’s wellbeing, but Frank doesn’t appreciate the gesture. Instead he sees Angus as cowardly (a trait he often associates with women, and therefore dislikes). Additionally, even though he is scared of his brother, Frank misses him and is excited to see him again.