Sorry to hear about your favorite newsgroup being disrupted, Wanda. Not knowing the details of what is happening, it's impossible for me to say why this person persists in his attempts to disrupt the group. But one thing is for sure. Although it may not be obvious to you or others in the ng, this person does feel connected. He is getting something out of his posts and the replies to them - though it's probably not the kind of thing you or the others would want from the group. To use behavioral language, his posting is being reinforced.
If everyone in the group feels the same as you, and they wish to quiet this person or encourage his posts in a more appropriate direction, they could either (a) not reply to him at all (extinguish), or, (b) reply only to his posts that sound appropriate (shaping).
If the group continues as it is, they are probably fueling his flames. As one of my old clinical supervisors used to say, "It takes two to tango."