I think they are refering to the natural inability of those espousing that we are just evolved ameobas, have no grounds to defend the sanctity of human life.By that, ah, "logic", I should believe in slavery because I know that my ancestors on my mother's side owned slaves.It is a logical link to make as you eat your hamburger.
Do you "OWN" a pet?
That is the great thing about knowing the truth; Christians can't be lawyered into being immoral imbeciles. (My dog doesn't wear a top, why should Janet have to?)