Well, "infinitely" might be hyperbole, but as far as why I say the Panthers were better than the Klan - I guess it would be that the Black Panthers were motivated by self-defense, the Black Panthers were not mainly driven by racial hatred, the Panthers were out to resist oppressors, not to further oppress the already-oppressed... I could go on and on. Honestly, I think it's weird to even have to give reasons, because it should just be obvious.
As I said, I'm not a fan of violence. I'm also not a fan of Marxism, and particularly Maoism. So, I don't really like the Black Panthers. But compared to the worst terrorist organization in the history of the U.S., yes, they're much better.