from Melissa Draper:

The Toes Clause
If you witness someone stepping on someone else’s toes; do not harangue the person with the bruised toes for being hurt, simply because you did not feel the crush. If you step on someone’s toes; apologise for stepping on their toes. Resist the urge to point to an inconsiderate witness, or people whose toes you have not yet stepped on, as excuses for not apologising.