My DH's family says LOTS of words wrong. For example, eating spaghetti means they are eating "EYEtalian" food. DH prides himself on being well educated (first in his family to go to college, etc.) and would never want to look uneducated, so I try to gently let him know later when some of those words come up. (I know - it sounds obnoxious, but he would REALLY want to know.) He always said that both (his family's way and the accepted norm) must be right, but I noticed he'd start paying attention and sometimes change his own pronunciation. It took until the internet became a thing and he could look things up easily and verify my opinion, that he finally just started believing me when I'd mention a correct pronunciation or grammatical rule. (And trust me, it's not like I know how to pronounce everything - his family is just particularly not gifted in that area!)
Again, I know it's REALLY obnoxious to correct people, but my husband would truly want to know and I also owed it to my kids.