reading through that, they were within their rights. part of the definitiobn as to the ruling was that the police were in pursuit of the suspect. basically, you can't turn round and run into your house and go "nya nya you can't arrest me".
further, it was a 911 call which means the police are ALSO required to think on their feet and act according to the situation. Given that the defendant in this case was in a seemingly agitated and abusive state, for the safety of all involved, the police were in the right to act as they did.
further note that in the addendums of the two dissenting judges on this case, that this was tried back in 1974. "The Court of Appeals reached the same conclusion over three decades ago. ―[A] private citizen may not use force in resisting a peaceful arrest by an individual who he knows, or has reason to know, is a police officer performing his duties regardless of whether the arrest in question is lawful or unlawful.‖ Williams v. State, 311 N.E.2d 619, 621 (Ind. Ct. App. 1974) (emphasis added)." So the court in this case is simply following the precedent set previously. also from his dissenting note "Indeed a respectable argument could be made that police response to a report of domestic violence is an exigent circumstance justifying entry into a home without a search warrant."
I think the two dissenting judges have the right of it in this case, and that the defendantwas pushing his luck too far in trying to claim he was within his rights.