(One of my principle focuses in providing polyamory educational resources is poly/mono relationships. I give a workshop on the subject and make the handout available on my website).
I must say, SITH's letter sounds for all the world like it was written by the poly partner instead of the mono partner, but if that is not the case, then this mono man's poly wife is a lucky person indeed. It's a challenge for many mono partners to take such a fair-minded stance, and understandably so.
SITH makes the point that it is bad for closeted gay people to deny who they are and uses that as an analogy to justify the importance of permitting a poly partner to live a poly life. Interestingly, this time Margo's response is to basically say that when it comes to monogamy, some feel one way and some another, but regardless .....
I believe the gay community will clear all the cultural and societal hurdles and prejudices long before the open marriage or polyamory crowds.
After which she signs off "Margo, psychically." Time will tell whether Margo has it right. The truth in that statement will largely depend on how much polyamorists are willing to support advocacy organizations like Loving More.
Margo Howard (daughter of Ann Landers) writes a syndicated advice column in which in the past she has (a) made erroneous statements about polyamory, (b) retracted them after the community wrote to correct her misstatements, and (c) more than a year later responded to someone in an MFM triad looking for a fourth a bit ascerbically but generally much better than the first time she addressed the subject. Today's letter is the fourth time she's addressed the subject of polyamory, and she certainly seems to be applying what she's learned, for which we can all be grateful. If you're willing, it would be good to write to her and say as much, as I am going to do.