I agree with your sentiment, but the Rams are playing this correctly. If he AD relents and signs with the Rams, he's only having to swallow the bitter pill of not getting exactly what he wanted. BUT, if the Rams publicly go hardball on him with fines and rescinding offers, that action could turn the pill simply too bitter for AD to swallow. Putting AD through public humiliation (even if deserved) gives the Rams no advantage.
They very well could intend exactly what you say, and have told AD as much, HOWEVER... they'll keep it private as long as possible. IF Donald relents, the negotiations can stay as private as Donald wants them, and the Rams won't have to come out looking like they were too rough on Donald, which might sour star players from joining or sticking with the Rams. (Again, even if he deserved it).
In other words, there's nothing the Rams gain by publicly denouncing Donald, and they could POSSIBLY lose the best player they've had since Bruce.