Well, if nothing else -- if being mind-whammied by HYDRA means Bucky isn't responsible for his own direct actions, doesn't being mind-whammied by Wanda *with the specific, malicious intent of making him overreact* similarly mean Tony isn't responsible for the Ultron incident, especially since he was *at no point* directly controlling Ultron in the first place?
The situations regarding Tony Stark in
Age of Ultron and the Winter Soldier in
Civil War are dramatically different in terms of actual control and manipulation. In that in the latter case, there was actual direct control of the Winter Soldier by HYDRA.
There was literally no control of Tony Stark by Wanda, only that manipulation of his feelings. It's obviously apparent that Wanda had no inkling or iota of an idea that Tony Stark would contemplate anything like the Ultron Project and while Wanda's manipulations upon Tony's fears might've initialized it, Tony Stark literally ran with the idea for the rest of the way.
With that said, the responsibility isn't fully Tony Starks (and Bruce Banners) and it can be partially attributed to Wanda as well.
While I'm not sure how much responsibility Bucky Barnes has, considering the extent of the mind control HYDRA had over him, it seems self evident that it's dramatically different situations to the point it's really a stretch.
And my argument is that no, he *doesn't* have sufficient evidence. He *wants* to believe that the HYDRA mind control is a "curable" issue and that the innocent Bucky inside the Winter Soldier can be rescued, but that was what he *wanted* to believe based on Bucky hesitating to finish him off at the very end of Winter Soldier, but that was only a *momentary hesitation* before the helicarrier exploded, and keep in mind that while the *audience* saw Bucky pull Steve out of the river after that, *literally no one witnessed that*.
Given the facts *known* to decision makers, and even the facts *known* to Steve, his belief is clearly motivated by personal bias and *not* any basis of fact.
Two years passed between
Winter Soldier and
Civil War with no more incidents surfacing regarding said Winter Soldier. Also keep in mind in
Civil War, Captain America went to grab the Winter Soldier for two reasons:
The FIRST reason he stated was because he felt he was the one that could bring him in without anyone getting killed. He was further motivated later when Sharon Carter flat out stated they were going to shoot him on site based on extremely nebulous evidence.
When the two super soldiers had their encounter in Bucharest, Bucky did absolutely nothing to make Steve Rogers regret the decision and within minutes of meeting Steve Rogers he firmly iterated that he wasn't going to kill anyone, wasn't planning on killing anyone and no longer engaged in that lifestyle, thus confirming ALL of Steve Rogers "personal bias" on him as being correct. He also surrendered to the Bucharest Police because unlike the noble and brave German Special Forces, they weren't ordered to 'shoot on sight.'
Nah. Wanda was a person who broke. That made her tragic and fallen. It was her choices AFTER the Vision died that were evil.
The argument might hold water 'in-universe.'
But this originated as a discussion of the films overall quality. Holding a films quality hostage to retroactive continuity based on television and movies that come out years later is just unfair in most respects. There's no way to predict such a thing occurring. No one involved in making the Captain America sequels was thinking "Oh I can't wait for Steve Rogers to be proven wrong and all of these movie themes crapped on when Multiverse of Madness comes out!"