Sorry, I'm on your Dad's side. I think the best way to teach your children to speak properly is to gently correctly their speech. I have always done that and people have always commented on what eloquent speakers my children are.
My dad overcorrects my 2yo's speech--how would you approach it? - Page 2
well, some kids do learn it naturally, and some kids don't. And some kids who learn it *naturally* are getting a lot of coaching. To me, it seem normal and healthy to model proper speech and to nicely encourage kids to repeat things back. I also don't think that every adult in a child's life has to do everything the same way.
But one of my kids spent a couple of years in speech therapy. She had to work hard to learn to speak. My sister believed that her DD would learn to speak naturally, and she's in 4th grade now and still VERY hard to understand. May be you can just ignore your child's speech patterns and have them go away on their own. May be not. Not all kids get it from just hearing it.
Are there a bunch of other issues with your Dad? I don't see getting worked up over encouraging a child to use the right name of the cereal and say please unless it's just one of those things that no matter what your dad did, there's just so much history there that he just ticks you off.
I don't think correcting a child's speech is inherently problematic, but it sounds like the OP's dad is being a tad obnoxious about it:
DD's nearly three and is (in my unscientific opinion!) very verbally advanced - she uses words like "complicated" and "hideous", has a good grasp of colloquialisms, makes sentences with complex clauses, etc. She still has her verbal quirks, such as pronouncing Vs and Ws (she calls DH a "pesky warlet" quite frequently), a la Ensign Chekov. DH sometimes corrects her, whereas I take the "But it's so stinking cute and she won't do it forever!" line. (Although it's also pretty amusing to hear DH saying "I'm not a warlet. I'm a VARlet. Can you say VARlet?" "Warlet!" "Varlet". "Varlet". "Very good!")
Because DD likes language, she doesn't seem to mind being corrected - she finds it amusing and likes to try to say new words. Plus, she's used to us being corrected all the time by our Spanish teacher! If she found it humiliating or upsetting, it would be a different matter. The OP's child doesn't seem to have too many issues from it, so maybe it's just one of those things that grates on the OP without harming the kid?
I agree with this. I think it's okay to gently correct a child's speech. OP, is it more annoying because you are living there? Maybe it would be less irritating if it were something you didn't have to hear all of the time?