Whenever I hear statements like "It was a great deal for he and I" and "Call Karen and I in the morning," I die a little. Such solecisms, as Twain said in another context (Cooper's prose style), "grate upon the fastidious ear." Moreover, I know that these things will likely become accepted usage in time, if that hasn't already happened.
As someone who tries to be careful with words and speech, I feel almost a moral obligation to hold the line against this kind of decline. I'm not a word snob; I say "ain't" when it works for emphasis, and so on. I've tried suggesting the grammatical alternative to the above constructions, but even when I phrase my suggestion in the gentlest possible way it never works well and I almost always wind up feeling pedantic and priggish at best, and at worst I feel I've alienated someone.
What's the general opinion here? Is it best to just let these things slide or to take up the fight? In sum, is there a good way to promote good grammar, or at least protect it from the most egregious violations?