Neither, really. They are just concentrating on California and ignoring the wider question of the United States as a whole. The argument is that the original Proposition 11 was a great good and that Prop 50 by contrast is anti-Democratic and turns back the clock to allow politicians to take power from the people.
I will note that back in the day while some prominent Democrats supported Prop 11 and the Republicans certainly did (and nobody donated more to the campaign than Schwarzenegger), the CA Democratic Party as an organization and major figures like Nancy Pelosi did not. It was all about whose ox was being gored and cynical national politicians like Pelosi were loath to surrender a potent tool like gerrymandering, while even-then-in-the-minority cynical CA Republicans wanted to make sure it wasn’t used against them. It ended up being a very close vote in the end.