Yes, I agree (although you cannot really blame Microsoft for this).
But, to be honest, someone who is able to install Linux should also be able to roam through the Bios (which he/she should do anyway to check the settings, e.g. confirm the boot sequence).
Plus, as far as I understand it, Linux can actually profit from secure boot, right?
Correct. But the steps to do so vary wildly from motherboard to motherboard and are not documented anywhere.
In fact, one of the things HispaLinux requested is that OEMs provide clear documentation of the technical steps required to disable SecureBoot.