I agree...I've seen it a few times. There is mention in the movie of Tyrell, "designing their minds", but I assume it was in the nature of improving what was there via "neural improvements" and memory implants. [I wonder how valid this concept of memory implantation is, however, after reading an article that postulated the brain's memory works on "holographic" principles (pieces of each memory are distrubuted), rather than on highly locallized collections of "data bits" you have in a computer memory.]
Even though they appeared to be cobbled together like Frankensteins (given the "cottage biotech industries" shown, like the eye-maker), I agree that being basically human, they deserve the full range of human rights.
PS. I have not read the book that "Blade Runner" was based on, and wonder if the novelist spells out the Replicant design in more detail.