It should come as no surprise that what touches off this spate of mutual recrimination is the very minor issue of getting Mike prised loose from the rec-room couch to set the dinner table. We know damned well that the imbecile thinks that he's this great big mature person who's too damned big and important to be a slave-boy and we know equally well that Elly rushes off to caterwaul to her fellow pea-brained incompetent failure Connie about how the by-the-numbers petulance of a stupid kid who thinks that having to set a table makes him the victim of all victims surpassing all others makes HER the victim of all victims surpassing all others. He's filled with nitwit hostility because he thinks that he's being treated like a mule and she loses her shit like the raging dough-head she is when he identifies her correctly as a loud-mouth with an overweening need to lecture people about how they're horrible monsters who can never please her.
The end result is that both people are both aggressor and victim at the same time and it's not their fault that they butt heads over non-issues. The less important a problem is, the more furiously they fight in order to distract themselves from the fact that when it really matters, they become paralyzed with indecision, doubt and fear. That's not their fault either because real problems that they need to take care of make them freeze up because they might be blamed for things if they go wrong. Since that can't happen, we can look back on their history and marvel that they didn't kill the fuck out of each other deciding on whose turn it is to walk Farley.