AFAIS, defense of anything is often a coercion, yes. There are millions of subtle situations for court to decide who, on the one hand, exercised his freedom and who, on the other hand, initiated a coertion, who responded to a coercion, and there is a room for interpretation.
Also, the core principle is not a set of laws, it's just a guiding principle. If a court interprets certain possessions of proprties or certain actions as an initiation of coercion on other individuals, than it can judge it unlawful. For example if you place a bomb near someone, or your property blocks an entrance for someone etc... that could be a coercion, AFAIS.
At the same time the core principle is akin to declaration of a constitution and as such it steers the lawmakers and society toward certain direction. But it's not an utopia that aims to describe everything by a single short paragraph.
Also, the core principle is not a set of laws, it's just a guiding principle. If a court interprets certain possessions of proprties or certain actions as an initiation of coercion on other individuals, than it can judge it unlawful. For example if you place a bomb near someone, or your property blocks an entrance for someone etc... that could be a coercion, AFAIS.
At the same time the core principle is akin to declaration of a constitution and as such it steers the lawmakers and society toward certain direction. But it's not an utopia that aims to describe everything by a single short paragraph.