Used to shrug off leftover waste as no big deal. Learning about landfill methane changed my mind completely. That gas is way more potent than carbon dioxide from cars. Now I get why every bit counts, like your friend's tossed meals. It's absolutely your place to say something because we're all in this together. Ignoring it just lets the problem grow.
Started bringing my own containers for leftovers when we go out. Made it a normal thing so now my friends do it too without feeling weird. Just takes one person to start the habit.
Yeah, I was just reading how food waste in landfills makes this methane gas that's way worse for warming the planet than car fumes. It made me look at my own trash can differently. If your friend is tossing whole meals, that really adds up.