You persist in holding the mistaken belief that, at the time of Pinochet's coup, the Chilean constitution was still functioning. Remnants of it were still functioning in the legislative and judicial branches, but those remnants were being forcefully overrun and ignored by Allende. By invoking the constitutional oath as a basis to arrest Allende they were invoking the doctrine of self preservation. Western legal tradition has long recognized that no constitution is a suicide pact, meaning an affirmative action that is procedurally unaccounted for in a constitution's text (note that the arrest of Allende was not barred by the Chilean constitution either though) may nonetheless be a constitutional act when it is necessary to save that constitution from complete destruction. The Chamber of Deputies' recognized that, and the strong endorsement of the coup given by virtually all non-Allendist officials in Chile served to affirm it.
But by extraconstitutional means and for extråconstitutional ends.
Western legal tradition has long recognized that no constitution is a suicide pact, meaning an affirmative action that is procedurally unaccounted for in a constitution's text (note that the arrest of Allende was not barred by the Chilean constitution either though) may nonetheless be a constitutional act when it is necessary to save that constitution from complete destruction.
Of course, that is not what happened. And you'd be hard-pressed to find an informed observer of Chile who would say that Pinochet intended to preserve the Chilean constitution. The fact that he didn't is perhaps the strongest evidence.
The Chamber of Deputies' recognized that, and the strong endorsement of the coup given by virtually all non-Allendist officials in Chile served to affirm it.
Sounds like you're favoring the tyranny of a politically correct majority over the rule of law.