The last thing that Grantaire wanted was to bring down Enjolras' high with serious talk. That sort of thing went south for most people, and this happy chief was such a rare sight that it was even more important not to interrupt silly things with serious thought. The barricade in the living room and the horrible red flag on the wall did far enough damage without any of Grantaire's help.
Distraction time it was then.
"Not insane. Safety first and all that. If you've been spending a lot of time in there, it's better to be more stable so it doesn't collapse on helpless Danton. Or yourself. It would be such a shame." To the question, Grantaire waved a hand dismissively. "No tea. Lead the way."