VCO brought up some good points. Pray about them. You just might find yourself in arguments that go nowhere. But on the other hand, if you would spend as much time praying for those people as you do trying to make inroads to their understanding, you might be going exactly where God wants you. I can see a need for more intercessors than preachers on such a site as this.
Those kinds sites and the non-believers that go there FEED ON VICIOUS NAME CALLING ARGUMENTS. Most of them have already hardened their hearts, and only go their try to make Christians look ridiculous, just to feed their own sick egos. I used to be a Volunteer Chaplain in California's largest Prison "HOLE" {Security Housing Unit}. So I have been called every name in the book, but was able to ignore them, because I prayed to be FILLED WITH THE SPIRIT every time before I walked through that front door. I learned to rejoice for the few who wanted to hear the TRUTH, and I mean the VERY FEW. Now if you are the type that cannot stand to be called Names, it is definitely is not a ministry for you. Because if you loose your temper one time, you will have fourteen of them laughing at you and calling you hypocrite, among some filthy names that I will not mention here. AND once that happens, your credibility as a Witness for Jesus Christ is totally blown. It was my experience that they really do attack like vicious wolves, when they sense a lamb is wounded. AND ALL THE TIME, you have to TUNE OUT the lies and tricks they use to get you to DOUBT your Beliefs. Jude warned us that when we went into get someone out of a cult, to snatch them as if out of the fire. Why do it that quickly, because I believe it implies that in lingering long, we are in danger of our own garment could becoming spotted. That means some of their bad habits and false teachings might rub off on us.
I have seen it happen to my son-in-law. He used to Read WATCH TOWER Magazines, telling me he could glean the good info in there and ignore the bad. Then one day when we were in a personal bible debate, he quoted a Watch Tower teaching to me, thinking it came from his own Church. That is how dangerous it really is. It is not a ministry for a lamb, and even a mature Ram is in danger. You have to stay Prayed Up, Totally KEEP THE WHOLE ARMOR OF GOD ON, A BE FILLED WITH THE SPIRIT at all times, and absolutely BE UNSHAKABLY GROUNDED IN THE WORD before becoming involved in a ministry involving the Cults. I would reread Dr. Walter Martin's book, Kingdom of the Cults first, and Dave Hunt's book the Seduction of Christianity second, and even Beyond the Seduction by Dave Hunt third; if you still feel called to that Ministry.