They were given a chance to admit they were at fault. They instead bullshitted about “sloppy work”. You just don’t accidentally take someone else’s work, strip their name and brand it as your own, and brag about “built in three days” or some shit.
And even if they handled it very gracefully afterwards, don’t expect everyone to be happy about it. That’s Mashimo’s problem isn’t it, someone’s gonna criticize regardless. No shit!
Btw, I have never ever taken someone else’s work and brand it as my own without credit, or cheat someone in any other way (or at the very least, never intentionally). Thank you for asking. I don’t think that’s a high bar to clear.