"The opposite of love is not hate, it's indifference." -- Elie Wiesel
The Witnesses would rather be hated ("proof" that they are spreading The Truth) than be ignored. If they were hated, that would mean they are important in what they believe to be the grand scheme of things. Indifference and pity affect the cult psyche more outright hostility ever could. Cults are about being special, about having something outsiders are jealous of. A shrug of the shoulders can threaten the cult mindset more than harsh words.