Vapaad was a style that treaded -close- to the Dark Side. In reality the only dark thing about it is that its so aggressive. The trick is not to be thrilled by the thought of death and destruction, but of winning. And Mace wasn't Dark Side! It was WAR, you pitiful excuses for Mandos (that's the people sayin Mace is evil; the hate is understandable)! It was a battle, and in battle the strongest warriors are the ones that come out alive. It was a battle of the heroes between Jango and Mace. And Mace won.
Jango Fett was a Mandalorian in every sense of the word. And I think that he would accept this. Certainly he'd hate having to leave his son to fend for himself, and he'd hate the fact he was dead and there was no more butt-kicking to be done, but he wouldn't end up loathing Mace for it and making any 'he's evil' accusations.
As for Obi-Wan, he knew that Jango had his boy to look after... did you notice he didn't fire back on Slave I? Mace didn't. If he had, I have to believe that Mace would have let him go if he could have. All he knew was that Jango Fett tried to have the good Senator assassinated. What would you have done in his place?
Rest well, Jango. We love ya.
"There is no greater good than justice," -Boba Fett