Not if it’s a stranger, no. I tried, when I first moved to a big city, but honestly became overwhelmed by the giant piles of garbage everywhere all the time anyway and the general extreme lack of care in everyday habits while professing diehard environmental values. Ah, NYC…
My friends and friendly acquaintances, yes. Especially cigarette butts – I’ll often point out that they count as litter.
Remember that incredibly frustrated, kind of horrified moment when you were starting out in watersports and suddenly realized your beautiful waterway is actually a sewer? I wish I could bottle that feeling and give everyone who litters a little taste. You get that feeling hiking, too – but I never really realized that all the trash eventually flows into the water before I started kayaking.