Tim,forgive me if this comes out all wrong.
He is partly right,if he just wants his carpets cleaned by purchasing a machine and you showing someone how to use it,the carpets would be cleaned,maybe not professionally but cleaned all the same,but if things went wrong for whatever reason he would no doubt hold you responsible.
Pretty much a case of this is a cc machine,this is what you put in it,this is how you work it and this is how you empty it.
But back to your main point,I would tell them to shove the contract as I could not work with someone with an attitude like that,but it is down to how badly you need the income.
John