There are several parallel discussions gong on. I think the questions are:
Was it OK to shot him because of the affair. Some people think that itself was sufficient justification
Was it OK to shoot him because he was advancing with a bat. (that is an interesting question of how far, what situation - input on how quickly someone can advance is interesting)
Was the bat story true? It seems a little surprising and I think a lot of people are sensitized by police shootings.
I don't think it's ok to shoot someone for having an affair with your spouse, but it does happen. Do I condone it? No. Do I understand the point of view of the betrayed who, in heat of passion, shoots an AP? Yes.
Was it ok to shoot a man advancing with a bat? Well, I suppose that depends on state law. Here, in my state, yes.
The devil is in the details. If the OM had to "go get the bat" there was a break in the argument, unless the cop chased him, which he shouldn't have done--he should've closed the door.
I would feel 1,000% different if the OM had the bat WITH HIM in the house and was coming at the cop when the cop entered his own home. Then the shooting would've been justified.
From the articles I've read it seems they were all outside when the shooting occurred. It hasn't been flat stated, but seems consistent with the description of the incident.
In my state, for example, the law states "individuals are allowed to use deadly force to protect themselves if they believe their life is in danger" and that "an individual has no duty to retreat if they feel unlawfully threatened by another
". Here, the shooting would have been legit even if closing a door had been an option.