[i speak in math]

People are defensive about things that they invest money into.

Photographers will spend a lot of money to get the body, lenses and flashes for their system. Since they are heavily invested in one brand, they will ignore many of the flaws in their system and choose to hate on other system users (We don't want cognitive dissonance, now do we?). However, they have not tried the other system because "trying" that system requires a new and separate investment, something they are unwilling to do.

So instead, they rationalize that the other systems is inferior to theirs. Anyone who uses that system must be inferior to them.