they’re not actually that big of plot holes if you consider just how bigoted this society is against supers.
Firstly, tony didn’t have a plan. I don’t believe either side when they say he was thinking about killing or capturing Bucky because that man was not thinking. From his lines and the way he’s brutally lashing out against both Steve and Bucky (his fighting here is reminiscent of how he fought against Killian in Iron man 3) tony is simply acting off of grief. Even the line “do you even remember them?” is indicative that he isn’t thinking properly because he doesn’t even respond to Bucky’s line: “I remember them all.” And the ending line of “My dad made that shield” / “You don’t deserve it” is just him lashing out. Tony didn’t have a plan, he was just lashing out at the people he blamed for his parents’ deaths.
To your point about Bucky being assumed guilty.
They were not in the United States. Not all justice systems operate on “innocent until proven guilty”, especially when there’s a Photo Of You Doing The Crime. And the photo of Zemo dressed up as Bucky made it pretty clear who probably did it
Because Nat dumped the files online, everyone knows about Winter Soldier’s kill streak. They know that he worked for Hydra, and he’s proven himself to be dangerous. Pretty much nobody but Steve and his circle would know that Bucky was brainwashed, the governments only knew he worked for Hydra.
The us government was freshly hydra-free. That manipulation and thinking would still be present in how they operate. Think about it like this
These countries just put the Accords in place, only to be attacked immediately by a superhuman threat. What would be a better way to show how beneficial these accords are, than to apprehend this threat with your non-super armies. The UN had something to prove in front of the entire world.
Not even mentioning the fact that everyone automatically believed the video mysterio made, proving that these people turn on their beloved heroes in a second. It might be Disney-etic writing but it could also be a way to bring a watered-down version of anti-Mutant bigotry into the movies. Most of these aren’t plot holes, they’re just signs of a corrupt people.
Team Iron man fans saying that Steve was wrong for not telling Tony that Bucky killed his parents but honestly, seeing how Tony handled finding out about it, I wouldn't have told him either. Tony was already willing to throw bucky into prison or an institution IMAGINE what he would've done if he found out bucky killed his parents while they still had him in custody. Steve was doing what he always has done, protect Bucky.
People openly supporting the revenge killing of a man who had NO control over his life for the past 70 years and wasn't even conscious for the majority of it because of something he did WHILE BRAINWASHED is insane to me.
(also please don't attack me I'm just stating my opinion TwT)