While I can understand the heat for Lackey w/r/t leaving his wife when she had cancer, I do want to say that there is probably way more to that story than we will ever know and I'm not sure it's particularly fair to assume he left her because of the cancer, because he couldn't handle it, or anything like that.
One of my girlfriend's close childhood friends died of cancer a year or so ago and we both went to the funeral. From everything I was told, this girl was just a delight of a person, had a big heart, was selfless, spiritual, the whole 9 yards. But she and my girlfriend hadn't spoken in quite some time because once she got the cancer diagnosis her personality began to shift and there started being a lot of tension any time they would speak, eventually leading to an unpleasant encounter where this girl basically told all of her closest friends to fuck off. There wasn't bad blood or any particular incident that caused the split, just the girl deciding that her friends did not see the world they way she wanted them to see it now that she had cancer and she couldn't deal with them any more as a result. A once tight friendship turned to basically dust in the span of a few months, long before her eventual death.
I don't know if John Lackey's ex-wife had the same thing happen, but I've heard of similar situations, where the cancer poisons the mind as well as the body and the afflicted person stops bearing any real resemblance to who he or she (etc.) once was and resent attempts to be supportive or helpful, sometimes lashing out at those who offer it, likely in fear, frustration, or something in between. If that's what happened and the two of them just lost any love they had for each other, I can understand why the divorce would come up.
Nothing about John Lackey ever suggested he was not willing to love his wife because she had cancer and it's possible their issues started long before; it has to be difficult to be married to someone who is on the road more than half the year and might have a port in every storm, so to speak (not saying he did, but no guarantee he didn't). But I can't hold something that happens in someone's personal life against him without all the pertinent information because I wouldn't want anyone doing that to me.
It sucks what happened, but heaping all the blame and guilt on him may not be fair. If someone has more info and wants to share it, it may change my mind, but I can't hate a man for a decision he made that I don't know enough about to say if it was the right one or not.