If they have similar attitudes to mine, then the feelings are slightly positive, possibly because of receiving validation for my own behaviour. On the other hand, if the defectors are doing worse things, the feelings are fully negative, I don’t think there is any effect as you suggest.
To put things more concretely, I try not to do anything harmful but also don’t do anything that helps society (charity, activism, environmental stuff, etc.) unless I get some concrete benefit. When someone does defect in the way of being actively harmful or breaking laws, then my emotions are negative as I said, but interestingly not as strong as in the case of activists. Perhaps because such behaviour feels normal and expected from other people, or just because it doesn’t feel as much like a threat to me personally.
So I would say that your second suggestion is correct in my case, I do have a sweet spot of cooperation (basically what I do and feel is justified) and dislike deviations from that, with heavier weight on the “more cooperation” direction.
I’m from Eastern Europe and have this tendency. I’ve been quite curious about why for example any kind of activism evokes negative emotions and I think at least in my case the answer seems to be what you’re proposing here. The prevalent attitude in society is to free-ride as much as you can and I’m also doing that. To answer the question from the beginning of the post, if we just let other people make cooperation the new norm, then I’ll be expected to cooperate too. I want to keep not caring about society, so I guess the actions of cooperators cash out emotionally as a threat to the status quo that I want to preserve.