Maybe the secret ingredient is human empathy. Not that crazies are unique to the right by any means, but the organized effort to dehumanize and attack segments of the population has gone disproportionately mainstream on that side of the spectrum. So many talking points involve a vaguely-defined "enemy" of some kind. It's unfortunate that people get sucked into it, but you can't really blame the individuals when the leaders they look up to are actively working to mobilize them in that way as a political strategy.
I guess the ideological space the left fills at the moment just isn't one that requires that type of anger to support. There are certainly issues to get angry about, but in general it's just taking that low-hanging fruit of giving your fellow humans the same respect you would want for yourself and your loved ones, even if they seem different or weird to you.