"Matsuda is being stupid again"

And we love him for it. Legit: According to some Matsuda was the philosophical counter part to Light that challenged his and L's dogmas or something XD

For real, in all honesty, he's the most reliable character in Deathnote by far. If not the best character in it. Like, I will legit never stop getting emotional over the ending where Matsuda snaps and just let's Light fuckin' have it! And the episode dedicated to him is honestly one of the better episodes in the series!

"Matsuda you idiot"

Like he was meant to be the guy questioning the high ethics proclaimed by Light and L. This supposedly also was why they gave him the part of going nuts at Light in the end. Because he was the "regular person" exposing that those speaking of high motivations are just like everybody else if not worse or something XD

The writer of the OG Deathnote revealed that he even considered L to be "slightly evil. Light and L were written as two sides of the same coin, as examplified by tons of dual dialogue and moments such as L referring to Light as his "only true friend"

As such none of the figureheads were very good people. And Matsuda was meant to demonstrate it. I mean everyone bullies the guy XD