>My definition of freedom is akin to your freedom ends where mine starts

That's everyone else's definition too. The disagreement comes from you having the underlying assumption that producing non-GPL software is causing harm, while other people do not share that assumption.

Everyone agrees that your freedom to swing your fist ends where my nose begins, because everyone agrees that punching me is causing harm. But a lot of people do not consider writing software to be causing harm, so they do not see a valid reason to prohibit people from writing software.