gentlesoul... I'm not a Christian (which I assume is what you mean by 'believer'), but I'll venture to give my thoughts, not as a co-religionist but simply as a human being.
If your purpose in being at this site is to convert people, then I suppose that yes, you may very well be "throwing your pearls before swine." Few people here accept Christianity; and what is more, any Christian theological ideas you present on this site are likely to be challenged (as this thread exemplifies).
If your purpose here, however, is to provide friendship and support to those who are leaving the Watchtower, then I don't believe that your time and effort is wasted. Whatever your religious and ethical motivations, kindness and compassion are worthwhile and praiseworthy. And who knows, perhaps you may serve as an example to some departing Witness that it is possible to be Christian without adopting the sort of attitude the Watchtower espouses.