It is not. Or, to be more precise, it is a way of working within the copyright system to uphold the 4 freedoms that they consider most important. But, important

It is not. Or, to be more precise, it is a way of working within the copyright system to uphold the 4 freedoms that they consider most important. But, importantly, abolishing software copyright would not give users the 4 freedoms. Instead, the goal of the Free Software movement would be to enshrine the 4 freedoms into law - for example, making it illegal to distribute software without making the source available, and to make it illegal to distribute hardware devices whose software can't be changed by the end user. Having copyright + the GPL is more useful than no copyright at all.