#tile setter

I'm really frustrated. My dad is an HVAC who now works maintenance and my mom is a nurse, currently one of the head honchos over a home care facility. My husbands dad works as a professional tile setter. He's done work in commercial and residential. He's good enough that he's done work in malls. My husband has worked alongside him for YEARS, since he was a kid. So he knows his stuff. And even if he doesn't, all he does is have to call his dad for a consult. Well my parents asked my husband (Nathan) to fix some caulking in two of their bathrooms. In doing so, he found a lot of shoddy work and a huge mold and mildew problem, particularly in the bathroom that me and my brother have shared since we moved in. Kinda the open communal bathroom of the house. Anyways, seeing this problem launched a huge remodel/re-doing of the tile and some of the framework, I guess. Anyways, my parents are completely discrediting my husband and acting like he doesn't know anything. He has a plan to fix it up to last them for eons, but they're dead set on doing a shit job because they think they know better. Yes, my mom the nurse and my dad the HVAC turned maintenance are suddenly tile experts. They'll ask him his opinion and what they should do, and then turn around and tell him he doesn't know what he's talking about and then do the literal opposite of what he says. They're sitting there listening to the SALESPERSON at the tile store over Nathan. They're sitting there referring to YouTube and Google before trusting Nathan and his dad. Like. Holy shit. Why are they being so stupid? Both of us are ready to throw in the towel and just let them fuck up their house like they want to.