I don't think this argument holds much water. First of all, in some poyygamous cultures, men marry several sisters all at the same time, so there's no "old" ones and "new" ones. Second, many times (theoretically) women could say - and think - that they like the arrangement. In fact, in the article posted above, the man went in to procure a marriage license with his current wife and the prospective bride at the same time. No protest from wifey #1 apparently.
Yes, exactly. I've been exposed to polygamy in many parts of the world, and in families that were well-educated and modern. The women are quite happy with the arrangement most times; it has its advantages. Having seen polygamy as practiced by many different cultures around the world first-hand, I have a hard time condemning it generally. It functions quite well, and some of the arguments I've heard, even from the women, are actually fairly compelling and rational. Or to put it another way, polygamous marriages seem to function as well as monogamous marriages, generally speaking, and have the same number of problems. Women that get involved in polygamous marriages are something of a self-selecting population and are usually acclimatized to the way those things work in practice.
I think part of the problem with the discussion on this forum is that people here are projecting all sorts of odd perceptions of polygamy onto the basic issue. It isn't like most people here seem to think it is. The people that do this in various cultures aren't clueless or evil, and there are many fine men and women in healthy and functional polygamous marriages. It may be different and "weird", but there isn't anything intrinsically broken or immoral about it conceptually and as is typically practiced.