For those wondering why a vampire would experience a gradual stripping of humanity, hopefully this can help put it in this perspective.
Remember that as a vampire, you are immortal. That is a crucial component. Your body never changes - each night you rise with the same hair, same scars, same fingernail length, same everything as the night of your Embrace. You never change, and yet the world around you changes a little bit each night. Before you know what happened, you've been around for 50 years. You still feel more or less the same, but the mortal society around you has drastically changed, probably 5 distinct times already since your death. Then even sooner, it's been 100 years, and that change in humanity seems even MORE drastic. You might think that you would keep up with the times, sure. But you've been around for 120, or 150, or maybe even 170 years already, and you've seen trends change so many times that you've grown numb to them - they are just something mortals do to occupy their short time on earth. Changes in fashion, language, geography, politics, even technology become irrelevant for a being of such age and wisdom as you. Why should you waste so much of your time on something so trivial?
By the time you've gotten to this point in your unlife, you've also committed thousands upon thousands of repetitions of an act that makes rape and grand theft seem petty in comparison. You've seen more pain, sadness, suffering and death than several entire generations of people could see.
Do you really think you could still feel really human?