Okay, I have not ever dated that much, is this a clear rejection of NOT LIKING the person?
NOTE I WAS NEVER THIS PROFESSORS STUDENT I JUST WORKED FOR HIS DEPARTMENT AS A MASTERS STUDENT.
Most Helpful Guy
No this is him directly telling you that he doesn't think the relationship is appropriate, not only is it school wise but for the fact that at one time he was your professor, so until you can get on the same level, he won't be going out of his way to push buttons. It was indirect in his feelings but his language says that he just doesn't want you in that fashion and he's trying to let you down easy by using his own apprehensions as a base. He does not want a relationship from you and you pursuing it could put your work and school lives at risk which he's been nice enough to point out, because likewise you could risk his as well even if nothing happens.
Most Helpful Girl
He's not interested babe... It could be a multitude of reasons... age difference, work, he could be seeing some one already (m/f)... I would just move on instead of trying to find a reason when he has given you one.