There really aren't hardly any liberals who want open borders, or borders so un-policed that they might as well be declared officially open. The only leftwingers I know of who advocate that are fringy left-anarchist types.
"#abolishICE" is NOT about open borders. It's about abolishing the whole Patriot Act, actually, and returning to the immigration enforcement we had before 9/11 (when we actually had far fewer undocumented immigrants), maintaining closed borders, and moving back to something akin to amnesty for people who've been here for a long time, with stuff like the DREAM Act.