I really cannot understand why some folk get so worked up about grammar; and I say that as someone with a Classics background, who had all the rules drummed into him from Homer right up to Fowler's English Usage.
Language is a medium for conveying meaning. If someone's grammar impedes that, it matters; if not, it doesn't. The way we speak and write is a product of our individual education, background, linguistic heritage, the circumstances and the intended listener or reader. It has diddly squat to do with anyone's intelligence, culture or worth as a human being. People who delight in pointing out the 'correct' usage should bog off and do something more productive with their time.