To a first approximation, nobody sits in the voting booth and tries to "pull the ladder up behind them". At most they're thinking about what might benefit them but (again, first approximation) nobody's sitting there thinking about how to screw everybody else. If that's your best understanding of anybody's voting logic, you might want to consider upgrading your understanding, because what you've got there is just propaganda. Propaganda I could trivially repurpose to fire against any ideology; believe me, liberalism is not immune to that either.
(After all, is it not an interesting coincidence how much we've been talking about "income inequality" lately even as liberals have been in control of the Presidency, the federal bureaucracy, and have at least split control of the other branches? And isn't it interesting how all the solutions to the problem of "income inequality" involve giving those exact same people more power? Only this time we should expect income inequality to go down instead, for... what reason again? How is giving more power (which is just another form of money) to the 1% controlling our policy and government going to solve our income inequality exactly? Clearly the wealthy liberals and those liberals who expect to be wealthy later as a result of their college degrees (many of whom are, alas, quite mistaken, but they're voting "correctly" for now so shrug says the 1%) are just pulling up the ladder behind them even as they tell everyone else how helpful they're being. I can fire the "pulling the ladder up behind them" propaganda at any major group you name.)
Your definition of "liberal" and mine probably do not line up too well, in no small part because I don't consider the mainstream Democratic Party to be meaningfully liberal except where required to include parties to get their votes. (Income inequality is an issue not least because the Democratic Party is a center-right organ controlled by monied interests.)
And yet, I have even less patience for those whose understanding of economics are "well, it'll hurt me a little, so it doesn't matter that it helps others a lot." Which I don't feel is an uncharitable description of the techno-fetishistic libertarian in action.
(After all, is it not an interesting coincidence how much we've been talking about "income inequality" lately even as liberals have been in control of the Presidency, the federal bureaucracy, and have at least split control of the other branches? And isn't it interesting how all the solutions to the problem of "income inequality" involve giving those exact same people more power? Only this time we should expect income inequality to go down instead, for... what reason again? How is giving more power (which is just another form of money) to the 1% controlling our policy and government going to solve our income inequality exactly? Clearly the wealthy liberals and those liberals who expect to be wealthy later as a result of their college degrees (many of whom are, alas, quite mistaken, but they're voting "correctly" for now so shrug says the 1%) are just pulling up the ladder behind them even as they tell everyone else how helpful they're being. I can fire the "pulling the ladder up behind them" propaganda at any major group you name.)