Thucy doesn't make "idle comments." He's a planner, and a strategist. I am certain enough that thucy is foul that I will offer myself up as an equal sacrifice (kill me first, then him, or kill him first, and then maybe you won't even have to kill me).
But at this point, if I'm right, and we find out thucy is foul, we get a lot of information based on who's speaking up for him right now.
Joker has, indeed, been at odds with him publicly, but he also by his own admission has sufficient experience in this game to know that if they're both mafia it's good to "disagree" early on to keep up appearances.
Killing thucy now reveals quite a bit. If he's a mafia, it casts suspicion on abge, joker, and y2k as potential next targets. If he's not a mafia, it shows YJ is an idiot and deserves to die, and helps to clear abge, joker, and y2k.
Is there any other death that will now give us more information *no matter how it turns out*?