Husband’s little sis giving me marital advice

So she is 20 years old I just turned 29. She lives in another country but we WhatsApp each other. My husband is known to be difficult and hard to please...he is the only boy and eldest is the family, he is 35. He is hot headed and has a huge temper. She was saying how she came to the states and stayed with him for two months and they didn’t argue or fight once. And she was like I will tell you a secret, she was like never argue with him and always tell him he is right even when you know he is wrong... 🤦🏻‍♀️ ....and I’m thinking WTF. Yeah that’s okay because your his sister and you’re not in a relationship with him nor do you fucking see him on a daily basis nor live with him 365 days a year ...I think it’s unrealistic ....the arguing sure that’s okay but everyone argues...but always being right is absurd ...what do you guys think

? Maybe I’m wrong and she is a genius . 🤷🏻‍♀️