Joseph,
The SA says that he is only talking about a case where someone does not want to marry at all. However, if he says that he is waiting for a good shidduch the bet din does not interfere. He does not say anything about forcing someone to marry a particular girl. In fact, Yeshayahu did not force Chizkiahu to marry his daughter. He simply told him that if he did not agree to marry someone he would die. Chizkiahu then suggested the specific shidduch. In any case, the Rema says that today we do not interfere at all. Your kal v’chomer is not a kal v’chomer. Someone who does not want to marry at all at any time is violating a Torah mitzva. Someone who is waiting for the proper person or circumstances (in Lithuania it was common for men to postpone marriage until relatively late in life in order to learn full-time without financial pressures) merely wants to wait to do it properly.
As for marrying off the daughter without her permission and your “age old Jewish tradition”, Chazal say not to do either until she decides that she wants the guy. So far as I know, the only times it was actually practiced were during the Crusades, when no one knew if it would be possible later, and in Yemen, where girls whose fathers died were forcibly converted to Islam unless they were married.
Lilmod, what is the difference between telling him not to marry a certain girl and to marry a certain girl? Why should he ask a bet din? RJS obviously did not think that he was required to do so. This is a matter of the spiritual connection between the people themselves. Their lives, thieeir decision.