well now ... let me just say a few things.
First off I am super pleased that everybody is getting into discussing the issues that the situation raises. I don't like writing pure fantasy where everyone roars off into the sunset holding hands and inconvenient truths are taken out of the picture. That is my biggest complaint about so much fanfiction in this fandom is that the remaining "exes" somehow seem to be pacified or are suddenly okay with Ennis and Jack's new life together in the AU's and there is no fallout.
In proceeding with my own original story, I have never believed that Colson was an innocent victim of his own sexuality, nor that he and his wife had ever handled their marriage, or their divorce, in any proper way - the most that can be said is that Colson tried to keep from saying anything negative about Laura, and a lot of that motivation was his own sense of guilt and bearing the burden of the failure of their marriage. It was doomed, and his homosexuality had doomed it from the beginning. So there is both guilt and hurt there, but not something that Colson can do a great deal about unless Laura decides to forgive him. The only thing he can change is his own happiness, and his relationship with his daughters.
However, one thing I wanted to point out is that he has discouraged his daughters from running away from their mother, pretty consistently. For selfish reasons to be sure: 1) he didnt want to suddenly become a full time dad and complicate his relationship, now that he has one that he is happy with and 2) he didn't want to upset Laura by alienating the girls from her and letting them just escape to start over again with him. And the same is true in this situation - he agreed to their moving to Tourmaline because his daughter Pam had been attacked and begged him in tears to help her get out, and this was fueled by a manifest failure of support by her mother. He could hardly refuse under these conditions, and he still is conflicted about it. So Laura blaming him for giving them an exit strategy is not really fair. He could have interfered a lot while he was still in town with them, and never did, so assuming he has decided to step between Laura and their children and try to alienate them from her isn't really logical nor sensible. He is doing the knee-jerk reaction thing to finally help out a daughter that was alienated from him for a long time herself.
However, psychologically speaking, Laura would naturally assume that is what he is up to, since she put a lot of energy into discouraging the girls from having an ongoing relationship with Colson, due to her beliefs about his perversion, and in order to mollify her own hurt feelings. She would naturally assume he is up to the same thing - hence her indignation. But it is in defiance of the facts.