Is NOBODY wrong in the post ? POST : I met "A" through mutual friends about 10 years ago, and we became very close. He was the best man in my wedding and we had a lot of shared interests and passions.

So eventually A’s wife left him, after a long period of steadily increasing toxicity in their marriage. Ten weeks later, A moved in with “M,” the new woman. I don’t believe he intended me to know this. Aside from some "let's get together sometime" that never came to fruition despite my sincere efforts, contact between us substantially ceased completely.  


Almost exactly a year later, A contacted me out of the blue asking to meet and asked me to be his best man when he married M. I didn't give him an answer at that time, but expressed several reservations which, over time, solidified into a hard pass. They were:

* A was presuming on a friendship that he had essentially killed by his own choices (not his lifestyle choices, but specifically his ignoring-me choices).
* Although I took into his account his repeated assertions that their relationship was much healthier than the one with his previous wife, and that he was very happy, everything else I knew from a distance was negative. A relationship that progressed extremely quickly to cohabitation presumptively tending toward marriage, while he was, by his own subsequent account, still a wreck from his previous failed marriage, and which had, once begun, and which had resulted in the severance of most of his other social relationships (danger signal!), and in which there were financial, practical, and, I’m sorry to say, professional reasons to stay in the relationship, left me with the impression that his decision-making was probably compromised. 
* Also, I morally object to premarital cohabitation, and he always had as well, which meant that he was now in a relationship which was inducing him to contravene his own stated morals and beliefs, another nontrivial danger signal. But also, even if he had undergone a moral epiphany and was ok with it, I wasn't prepared to endorse it.

In a subsequent conversation, I told him that I'd stand up in his wedding on one of three conditions: That the couple make other living arrangements until the wedding (then some 8 months distant), or that they immediately get married by a judge, or if their premarital counselor could convince me it was wise. He promised to consider these and discuss them with M.   
 I'm not sure whether he considered or not. We continued to interact casually, but eventually he called me up and told me he was up against a deadline for tuxedos and needed me to answer one way or the other. I told him my concerns had not been dealt with and that unless he had new information for me, the answer was still no. I attended the wedding as a guest. And I've been struggling with the decision ever since. AITA? 