How would you react if the person you really liked told you they were afraid of a relationship with you?

I would interpret that as "I'm not interested." If someone then went on to say that they were feeling insecure, I would assume that either a.) they actually were insecure and would require an exhausting amount of reassurance, b.) they were fishing for compliments, or c.) they were making excuses because they didn't have the guts to tell me that they weren't interested. Any way you look at it, it would be discouraging.