I would think that there can be many approaches to taking this particular phrase and its meaning in the work. The idea of Smith's "love" towards Big Brother is quite the opposite. It simply means that he has stopped resisting the government. Throughout the novel, Smith's development as a character has emerged through his desire for freedom and acting against the authority structure. Yet, with his brainwashing, this part of him has died. In the end, his "love" for Big Brother is actually quite the opposite. Love would imply complexity and intensity of emotion. Rather, this "love" is simply acquiescence. He no longer lives his duality of resisting the party as this has been overcome and with this overcoming, "love" results. In the end, this contains dark and sinister overtones because so long as surrender is evident, individuals can be deemed as possessing "love" towards the government.