MLC is not an excuse for bad behaviour. It may be a cause, and they may be hurting, but you know, this behaviour is dishonest, rude and hurtful.
I agree with Linda that there may be hurt, and as you say, there are conflicting emotions. Compassion is good, but we also need to feel the anger that comes from being treated horribly. Anger is a healthy emotion that needs to be acknowledged. not a good place to remain, but a necessary feeling to experience and acknowledge.
Your h is acting in a passive aggressive way. In his mind he isn't married to you any more, but the reality of the law is that he still is, and until he decides on a divorce this is adultery from where I am sitting.