If I celebrated the death of everybody I thought slowed the progress of humanity, I'd never stop celebrating.
If I celebrated the death of everybody who ever said something vile or stupid, I'd never stop celebrating.
If I celebrated the death of everybody who supported political figures and policies that resulted in death and human misery, I'd never stop celebrating.
If I celebrated the death of everybody who decried racism, sexism, homophobia, and bigotry when practiced by the other team but brushed it aside as not a big deal when it was his or her own team, I'd never stop celebrating.
Hell, even if I celebrated the death of everybody who actively, as an actual politician, placed us into ill-advised wars, expanded state powers that they shouldn't have, and really were the ultimate causes of needles death and slowing down human prosperity, I'd never stop celebrating.
Maybe that sounds nice; but, it sounds like a really dark, vacant, self-absorbed life to me. I'd be spending my life celebrating the grief of others. In order words, I'd be an asshole.
If you're talking about somebody like Hitler or Stalin or Castro, yeah, I'll be happy that anybody like that is dead. It's still hard for me to take joy in it.