I agree that lack of fortifications does not mean lack of violence. This is all interpretations of what is left. Also, it is not impossible that these open spaces were "under the rule" of one of these "proto cities" who gained some sort of hegemony.Lack of fortifications does not mean lack of violence.
Iceland of Sagas and Norway of Viking Age had raids like burning of Njall, yet did not build forts.
Irish had endemic wars and sometimes built ringforts... yet 12th century witnesses say that the warriors lived in unfortified halls and disregarded the "Daneforts" visible in their landscape.
For small villages of 20...40 souls total, 5...10 adult men who often had to be away in fields, the cost-effectiveness of building and then manning fortifications is problematic.
An Archeologist (Michael Kunst, I think) hypothesised that the the "chalcolithic civilization" was violent and decentralized: independent proto cities competing for resources. And what came after, the Bell Beaker culture, was a more centralized society, with people living in small groups in rural areas, under the central authority of a single "proto city". This central "proto city" was never found. Kunst speculates that maybe it is located in what is now Lisboa.
Maybe there never was such a central "proto city", but one thing seems evident, there are much more signs of organized violence in the "chalcolithic" than in the "bronze" age in western Portugal.