The fact that this offends you does more to validate the position you are decrying than anything.
Also, just the term "black panther" and it being used to celebrate black identity is kind of significant on its own, since so many people have been taught growing up that a "black panther" is a evil, black supremacist terrorist or thug (as opposed to a coalition of black people trying to advocate for their communities in the face of varying levels of racism).
Do you have any black friends, especially one that is into super heroes? If you do, maybe ask them its significance to them, instead of writing it off as silly.