A list of filibusters for causes that today seem justified
That's a tall order. The best I can come up with was Senator Wayne Morse (I-WA), who filibustered a bill in 1953 that he thought was poorly drafted (Tidelands). Though he lost, he was proved right - the laws were indeed bad - for all state taxes on offshore oil after these laws passed had to be put in escrow until the courts could fix all the flaws, finally doing so via the Supreme Court in 1960 (SCOTUS: 363 U.S. 1 - United States v. States of Louisiana, Texas, Mississippi, Alabama, and Florida). Note this was before 1975 (when the change from 2/3 of Senators present and voting to the 3/5 of Senators sworn was made); i.e. back when you actually had to speak on & hold the floor, Mr. Smith style.