I went to watch this episode to see what you mean, and I barely call that assault. He simply bumped her. He didn't flat out hit her or handle her like she did him in return which was complete overreaction. I guess you can say he was sneaky in how to get her in their custody knowing she would react so defensively, but it could have been far worse. He's no Mike Logan or Elliot Stabler who have done much more to get what they wanted out of a potential suspect. In the end, it turns out the woman didn't even do the crime, but for the time being she did come off very suspect. For the most part, Cyrus is fair and a chill dude. I had no issues with him as a character during his time on the show.
Off-topic, but the format of the episode is rather interesting. I like it when the police and lawyers are more involved together during an investigation and it's refreshing to not see an actual trial happen. The show should have been more like this because for there to always be a trial, and very quickly at that, just got ridiculous. We needed more episodes like this to balance out the trial based ones.
He gave her a shove. That's not really assault. He of course knew what he was doing because it was clear he was trying to get her to attack him and it worked. But like I said, it could have been way worse. It was just tame enough for him to avoid a charge if it came down to it.
Well that needs to change because that is practically harmless. We'll be having a whole bunch of charges if that's the case and for the ones that do get made, very little about it gets done because of how meaningless it actually is. I remember watching a reality show where a woman got arrested for spitting on someone which was seen as "assault". Is it wrong? Yes, but not to that extent.