So wondering, if during a pre-screening interview I went on some rant along the lines of "I think the justice system is bullsh**t, they won't even let me smoke weed!", would that disqualify me from any jury, or just drug cases?
You can do better than that. One of my law partners during voir dire
states that he as a matter of conscience in PI cases, will not award pain and suffering damages. That does the trick for those kind of cases. You might also say as a grand unified disqualifying that you believe in jury nullification, and will not convict if the penalties involved shock the conscience (as they typically do in drug cases for example, but it goes beyond that). This old right winger actually subscribes to the jury nullification concept myself. Shocking isn't it?