I will ask you a question? What has your husband got to lose? The result of a stone getting stuck is possibly surgery. Who is your husband planning on seeing - a surgeon! So what difference will it make! Give it a go and then determine whether he still wants to go or not! Mind you one flush is usually just the start as you are conditioning your body to clean the rubbish out. Larger objects is going to take more effort and eventual dilation of the ducts. Flushes exercise your ducts with the intention they dilate better in time to cope with larger objects.
The flush is no big deal, sure the taste may be a little unpleasant but thats a picnic compared to an operation and possible after effects that DO NOT go away since you cannot grow a new gall bladder (yet).