An accusation that an assault took place 30+ years ago is going to be difficult to prove. There is unlikely to be any physical evidence after all that time and as unreliable as human memory is, relying on witnesses after that long of a time is going to be shaky. A fair society presumed innocence unless proven otherwise, and fortunately our justice system is based on that principle. With all of that, Kavanaugh has not been shown to be a rapist and only a partisan would call him that at this point.
What is fair is to criticize him for many of his statements during his confirmation, many of which seem to be false, inaccurate, or at least not entirely truthful. That should call into question his integrity.
That same principle regarding the presumption of innocence should apply to Dr. Blasey-Ford as well. Her accusation may be unproven and may not be entirely accurate (see the above about memory), but there have been no reasons to doubt her motives or sincerity. Attacks on her are unwarranted.