The Ties that Bind
It frustrates the hell out of Wally, being treated like child. He's held his own for years. He has his own set of Rogues, and while they may not be as deranged or malicious as the likes of the Joker or Lex Luthor, they're no walk in the park.
Ralph gets where he's coming from, but it doesn't really help much. Being constantly interrupted, having his opinions dismissed before he can even articulate them really wears on Wally's patience.
Though he doesn't like to think about it much, it also worries him. It's the first step on a slippery slope.
It isn't until Wally leaves that J'onn realizes his error. Wally has always done his best to stay faithful to the reasons for the League's existence. He believes in helping people.
Even when it could only bring harm in the long run?
Even then.
When Wally and the others return, laying out their plan to retrieve Oberon, J'onn realizes what he has forgotten: Wally is smarter than he acts. He considers the greater good, and comes up with an appropriate plan for all concerned.
J'onn promises himself to remember that perhaps Wally sees more than the rest of them, sometimes.