It helps if you're not vague when asking for clarification and quote what the issue is directly, the made-up quote doesn't really help if you wish to get an actual helpful response.

people should be friends with people who litter, and politely encourage them to improve their behavior?

My response: Make friends first without requirements

Or that they should walk away from people that litter?

response: Learn who they are and why they do things before passing judgement. From there, evaluate what kind of relationship you want with the person going forward (is this a co-worker? Someone from a friend group? What kind of relationship is required to move forward)

You can make friends...then unmake if necessary. If that's your confusion.