We should totally endorse secure boot for "webiances." I have to invent a word here because we haven't coined one yet, but its a device you use to surf the web, read email, chat on facebook, edit our resumes, Etc. It is something hobbiests and experimenters never ever need to write code for. Its the thing our grandparents use and we don't have to worry that Rico from Brazil is going to clean out their accounts with. It is an information telephone/tv/typewriter, it is an appliance.
Few people complain that you cannot boot unsigned code on the computer in your BMW, that is a good thing, you want to trust your car.
That said, there should always be (and no doubt will be) computers that engineers, hobbiests, and others use which are completely programmable. Those will be distinguished as being "General Purpose" computers as opposed to "Task specific" computers. They may even share the same instruction set architecture with their counterparts, but it should be perfectly Ok for a task specific device to refuse to run any code that hasn't been verified though some system of trust.
The comments about unlocking phone bootloaders, or the iPad, are quite relevant here. Those devices, when locked, aren't general purpose computers. Locked they can be task specific and reasonably safe [1]. Without such barriers they put their users at unnecessary risk and for users who have neither the ability nor the time to understand the risks that is a good thing.
[1] "reasonably safe" - This discussion will often jump to 'nothing is 100% secure' which is true of course and not the point. Planes fall out of the sky and kill people, but they are 'reasonably safe' which means that the risk of them killing us is acceptable given the benefit returned. Similarly with cars. Computers these days are not 'reasonably safe'. Huge swaths of non-technically literate people are harmed every year by the inability to create a reasonably safe environment for them to use.