A social system where software owners can dominate and divide users is a bad system. A social system where a few people become very rich while the others have a hard life is a bad system. The details of the issues are very different, but the spirit is the same. Property rights are a useful system, and I wouldn't want to abolish them. But when employed too strictly, they cause suffering, so we mustn't do that either.
Property is a useful tool for promoting human happiness.
But we need other tools as well, such as the welfare state. Libertarians elevate one of these tools above human happiness, and human happiness suffers as a result. Since the US abandoned Liberal policies, life has become harder for most Americans, especially the poorest-even though production has increased. These are my personal views only. Libertarians are welcome in the Free Software movement, if they support its goals.