Quote 7
Then the beautiful eyes of the fair woman open and look love, and the voluptuous mouth present to a kiss—and man is weak. (27.29)
Van Helsing explains why the Brides of Dracula at the Castle have to be dealt with—they're just too sexy! They can seduce any man. In his opinion, no woman should have that kind of power, so he's going to step up and kill them for everyone's good.
Quote 8
Yes, I was moved—I, Van Helsing, with all my purpose and with my motive for hate—I was moved to a yearning for delay which seemed to paralyse my faculties and to clog my very soul. (27.30)
Even the great Van Helsing felt the sexy power of the "weird sisters." Of course, he gets over it, and stakes all three of them.
"If so that, then what about the others? Ho, ho! Then this so sweet maid is a polyandrist, and me, with my poor wife dead to me, but alive by Church's law, though no wits, all gone—even I, who am faithful husband to this now-no-wife, am bigamist." (13.85)
If Arthur "married" Lucy by giving her his blood, then she's married to four people. Van Helsing finds this hilarious, especially because he's already married, and his wife is insane. Wait, why is that funny?