Does he actually think a word, said however forcefully, is going to stop someone bent on sexual assault?

How about you go in, say, "I'd like to punch you, yes or no?" He says, "no," you punch him anyway, and then tell him "you should have said no more forcefully."

(Actually I probably would not go back. I could accept careless words, maybe, although I don't see how your quote could be careless words, but not a lame-o "I wanted you to have more agency." That's just CYA, putting the therapist's ego before the client's need.)