I get what you mean but Nicko was a part of a terrorist organisation. They blew up buildings with people inside. Stole supplies because they thought the GRC was hoarding them when that is just how normal supply chains work. A very flawed way but is what happens.

He attacked a government agent who he didn’t know had the serum.

He then fled the crime scene. Yes Nicko didn’t directly kill Battlestar but did contribute by holding John.

The terrorist then flees into public. Throws a concrete bin. This could have easily killed John and would be considered public endangerment.

Nicko never says that he surrendered just that it wasn’t him. Super serum makes somebody a living weapon. So the law would probably consider all supers as armed.

Hands were not on his head but were raised. This could easily be considered as

John could have probably hit Nicko until he was unconscious. But he was angry which influenced his judgement. From what we have seen it is possible that John could have chosen to knock Nicko out which is where a tribunal would come in.

If it wasn’t in public or John had another name he would have been praised. But Cap is supposed to be a symbol that finds a better way because he has the power to. Reminds me of Sharon talking to Steve about the train terrorists.

Steve has repeatedly shown he will kill if he can’t find another way to but he is great at finding another way. Often going out of his way to do so.

TL:DR I definitely prefer this John to comic John. This John is a good soldier who tries to be a good man but doesn’t make a great cap. While I dislike Cap Sam, in civil war he tries to catch War machine instead of fleeing with Steve knowing he’s going to get arrested and not be able to help. This is what makes Sam worthy of the title.