Can we please take a moment to appreciate this scene?
Luka's anger came not only from the fact that his band's work had been stolen, but mostly because Bob was threatening Marinette!!! He only had strong enough negative emotions once her career and future were in danger. He wasn't thinking about his! He kept thinking about her at all moments! This shows just how deep and pure his feelings for her are. He doesn't have a mere crush. He loves her.
Just like in Chameleon, when he was talking about Marinette's righteous anger, Hawk Moth nailed his description: "The rage of a creator whose work has been stolen by someone a little bit fussy and who can't stand them making the one he's in love with suffer. Go little akuma, and evilise his pure heart."
(Sorry if the translation's not perfect, I'm not as fluent in French as I am in English).
Thank you, Thomas Astruc, for blessing us with his existence. We are not worthy