Good post, good read, awful OP.
I get where they're coming from on all counts. They can't pretend shooters haven't changed since Halo 3, and the audience has changed with them. Do I like sprint? No, but I also don't think it's the end of the world, and a huge part of their audience wants it. So why not try and make it work? Besides, like JdFoX187 said, Sprint is far from Reach and 4's only problem.
And despite statements to the contrary, people do care about feeling like a Spartan. They want to be fast, powerful, and accurate. All of these are very much Spartan-like traits. For some reason, "immersion" is a dirty word around here.