Technology

They don't like it because it's mostly implemented in microsofts favor. It's shipped with microsoft keys by default and needs to be disabled to boot a lot of linux distros. If there was a more unbiased way to load a new os like a default key setup routine at first boot or a preinstalled key for major linux distros they wouldn't be so hostile towards secure boot. The technology isn't bad and it's the only way to not have somebody temper with your system at rest without TPM.

I don't speak for all Linux users, but it's not like we don't like the tech or the concept... We don't like it because a lot of the time it's just another way for Microsoft to throw around their weight, you need a valid key to sign your kernel images with to be able to boot another OS instead of Windows, and some motherboards don't support installing your own keys as trusted keys. But usually there are ways around that issue nowadays.

And also it's not an easy process if you're not an advanced user of sorts. You have to know what is entailed, what to use, where to store your keys safely, have a script to re-sign the kernel image every kernel update(which happens every week on something like Arch), etc.

Which is dumb. Secure Boot does make sense (if handled correctly, unlike here).

Speaking from my background, it prevents someone from trying to boot using an external device to access your system, assuming you have a BIOS password in place.

Of course encrypting your drive works just as well, but security in depth demands a “why not both?” Approach

It's supposed to prevent unsigned files from being loaded by the UEFI (AFAIK) which could possibly help with rootkits, if it doesn't somehow sign itself. However, these are pretty rare if you don't allow sketchy software to access your boot partition, and will often cause issues with non major Linux distros.