Why are people breaking copyright law, instead of questioning the researchers who voluntarily approach the journals? Why not ask the researchers if they'd consider sharing their work? Or convince them of an alternative means of publication. There is no one-handed clap.
Besides being the main source of academic esteem, there is a serious structural issue where Elsevier et al receive publicly-funded knowledge, yet privately control the supply. The model seriously warps the production of research (and, arguably, the reproduction - p-hacking, fiddling with your regressions/covariants).
Using Sci-hub can be considered a form of protest. Perhaps 'break copyright law' is not a universalisable rule in the spirit of Kant, but the same is true of most forms of activism.