Having a fringe lunatic as plausible opposition actually works really great in a two-party system, as the Democrats can really focus on policy for lobbyists and not so much on policy for the electorate. Just point out that the other guy would be worse.
It's even worse this time, Kamala is running to the right of Trump in 2016 regarding Immigrants, so you can see in real time Trump jump to go even further right, like the cats and dogs bit.
Which of these candidates do you think will be more willing to have their minds changed with protests and petitions?
Nothing is going to be easy or perfect, but we can at least choose the most likely candidate that is slightly more aligned with our desired outcome and then fight for what is needed.
My dad gave me a choice between a pair of skates or a 10 year old used car when I turned 18 but I refused both and told him I wanted a brand new car. I ended up with a pair of skates. Getting to work was hard the next 4 years.