The literal combination of these characters—“to wear small shoes”—paints a vivid picture of constant, low-level discomfort and restriction. This metaphor perfectly captures the experience of being targeted by this kind of subtle harassment. You are being constrained and made to suffer in a way that is hard to complain about directly, just as complaining about tight shoes might seem petty.
This idiom highlights a preference for dealing with conflict indirectly, a common aspect of social interaction in many East Asian cultures.