It is my job to know grammar. I teach college-level English and I studied writing throughout my college and grad school careers. I even have a few books on grammar as it is necessary to know style and punctuation as a writer. However, I’m not the grammar police.
It has recently occurred to me that most people obsessed with grammar care less about saying something well than they do catching someone in a violation of the English language. They are superior little snots. Also, they are the type of people who would fastidiously avoid ending a sentence with a preposition. Their sentence are clunky because they have correct grammar, concision be damned. Then again, these are the people who obviously suck at math and take out their insecurities on others. Subscribing to a language dogma somehow makes them feel better about themselves as they are incapable of adding, subtracting, multiplying, dividing, and solving equations. That would take real mind work and knowledge.
One important thing to note is the grammar-obsessed rarely teach English or writing. They’re often not even linguists, who actually take classes on this type of stuff. They are often rank amateurs who often don’t know what they’re talking about. They may even have a dangling modifier in their sentence and might not even know it.
Self-appointed grammarians, leave this stuff to the professionals. Thanks.
General advice: DO NOT ENGAGE. They are the type of people to put up a fight, especially if they’re wrong, because, the burden of proof’s on you. It always is. Christian Lander has some further advice in his post about grammar.