The fair housing act definitely doesn't protect short term renters staying in someone's home.
"The Fair Housing Act applies to landlords renting or leasing space in their primary residence only if the residence contains living quarters occupied or intended to be occupied by three or more other families living independently of each other, such as an owner-occupied rooming house."
I.e. it doesn't apply to my parents renting out their basement apartment. However, many properties on AirBnB do not meet the requirements for this exception because the other does not make the property his residence. Under 42 U.S.C. § 3603(b)(1), a single family house is not excluded from the act (after December 31, 1969), if the rental is achieved through the "use in any manner of the sales or rental facilities or the sales or rental services of any real estate broker, agent, or salesman, or of such facilities or services of any person in the business of selling or renting dwellings . . . ." I don't know if AirBnB falls within that (broad) language (see subsection (c)), but if it does, it would be illegal to discriminate in the renting of a house you own for the purpose of renting it out on AirBnB (which is becoming more common).
In any case, my point is that when you are discriminated against by a hotel, at least you have legal recourse. As you point out, unless an AirBnB host has a property he owns for the purpose of renting out, you don't even have that.
