Landlords, Tenants and Mold

I got an amazing call from a guy in San Rafael this morning. His daughter has been renting a home for about six months and recently noticed that the floor was sagging in front of the dishwasher. She has a 12 month old baby and is currently pregnant. She did some additional investigation and found significant mold growth inside the lower cabinets and on the wall behind the dishwasher. The deterioration was so bad that the drywall was falling off and the framing behind could be removed with your fingers. They called their landlord, who is also an attorney, and he siad he would be there at 1:00 pm to check out the damage. I recommended that they contain the damaged area before any demolition of the damaged materials. They guy called back after his meeting with the landlord and this is where the story gets interesting. The landlord used a framing hammer to bash out the moldy material and told his tenants that there was no problem and that mold could not affect your health. He then wiped a huge section of black furry mold with his finger, and proceeded to smear the mold all over his lips like it was Chapstick. He said "see, its harmless".  Now, I was not there, and I didnt see any of this, but If I had I would have called this guy a @#$%ing idiot!  On top of all that, the landlord said that he was under no obligation to fix the plumbing, since the rental agreement required the tenant to make all repairs to the structure... IS THIS LEGAL?  How can a tenant be responsible for fixing or replacing old plumbing? I would be hesitant to ever rent from an attorney after hearing this story. I would, at least, read my contract very carefully.