Liberals have the reasoning skills of young children. They are easily manipulated into extreme positions through use of emotive symbols and appeals to their moral narcissism. That is why they are able to change their "core" principles 180 degrees in a short period of time without any embarrassment. As just one example, Bernie Sanders was an anti-immigration hawk not that long ago on the perfectly reasonable ground that immigration hurt low income citizens. Now he demands open borders as a matter of moral necessity.
In addition, liberals cannot just vote for someone. They have to turn them into some sort of idol who represents all that is good and admirable, while frantically demonizing their opponents.
These traits are very dangerous because they lead to rationalizing all sorts of bad things, from election fraud ( anything to stop the evil from taking power) to violence and persecution ( after all, they are evil and deserve it).