Here's my reasoning as to why including easy modes in game franchises known for their difficulty pisses people off. People like to brag! Yep, that's pretty much it. I see topic after topic about Dark Souls 2 getting an easy mode and Fire Emblem getting a casual mode and some gamers freaking out and others that can't see the big deal. The deal is that when a gamer beats a brutally hard game, they get to revel in the bragging rights which that accomplishment entails. When a game has no easy mode option, there is no doubt to the accomplishment's validity. However, when a gamer brags about beating a game with an easy or casual mode, even if they didn't use it, just the fact that the option is there is enough to invalidate the win in the minds of anyone they would want to brag to.
An example: When I was a kid, I actually beat Battletoads on the NES. You can bet I bragged my ass off. Now imagine that Battletoads has an easy mode option that slowed down all the vehicle session and chase sequences to manageable speeds, reduced damage taken from enemies, reduced enemies HP, etc. Were that the case, everyone I bragged to just would have assumed that I used the easy mode to beat it just like they would have had to. That's just how peoples' minds work, fair or not.
An example: When I was a kid, I actually beat Battletoads on the NES. You can bet I bragged my ass off. Now imagine that Battletoads has an easy mode option that slowed down all the vehicle session and chase sequences to manageable speeds, reduced damage taken from enemies, reduced enemies HP, etc. Were that the case, everyone I bragged to just would have assumed that I used the easy mode to beat it just like they would have had to. That's just how peoples' minds work, fair or not.