Afaik, libs are of two flavors: Firstly, the ones that are libs because cons are worse and think libism is the only solution. For them, Bidoof may be a horrible person, and the Dems may be terrible and corrupt, but there's nothing you can do except 
So, they Because they hate Trump. They may even agree with us lefties on all the social issues. But they think cumminism is bad and evil like Drumpf because they grew up in a Cold War world and are scared of Russia/China. Eventually, some of them can come around to accepting socialism over capitalism, especially if they have a heart and see all the bad capitalists and capitalist countries do, and you answer their very basic questions around profit-sharing, investor risk, etc. They're not that invested in capitalism as an economic institution. But it's still a slow and gradual process.
Second, the ideological ghouls. These are rarer but they're in it for the money. There's no convincing them. In fact, they'll be the ones convincing the good-hearted libs that we are agents of Drumpf and Putin. They may be managers or owners or other people who have or want loads of money and power. Be wary.
TBH, populism is bad when that populism is just a cover for right-wing puppet governments who push austerity and anti-immigrant measures to please their billionaire backers.