I'm just saying that Steve Rogers doesn't handle things that don't go his way as well as Marvel likes to pretend he does. Oooooo super military man, change in a second on the field, faced off super bad guys, both magic and non magic, with his rag tag group of merry men way back in the day.
He shits on Howard's son as soon as he's told about who he is based off of one person's opinion and his own biases about no one being able to match up to Howard... and continued to do so throughout the mcu. You're allowed on the team Tony, but make no mistake, you're only here as an outside consultant. And for money. And to live with you. And for your resources. Shield said so. He constantly boomeranged between treat his probably-would've-been-godson-had-things-turned-out-differently in a decent manner, use him for money, or treat him like shit. Tony, you belong here on this team... until you disappoint me, and then you're nothing; you're just useful for your money and your suit. We need you, Tony
Just found out your best friend is actually alive? Faced with unimaginable trauma and torture and doesn't remember you? Yeah, that's not his fault, but I'm going to force him to be the old Bucky because that's who he should be, causing a global international incident, and blame it on the one rich person in the group to clean it up. Meanwhile Bucky is traumatized, vulnerable, and trying to remember and relearn how to be a human - let alone function - and Steve totally takes advantage of that.
Then, when everything comes to a boil, and Tony learns that Steve knew about his parents' murder via Bucky and snapped, Steve still kept being a fucking asshole. Steve has trained with Tony for years. He knows how to handle the suit. He knows what the arc reactor does. He made the choice to kill Tony, and Bucky - poor fucking vulnerable Bucky who knows full well that it wasn't going to end well but wanted to make things right, didn't know how to or how to deal with things, and who's basically been influenced by only Steve and his merry band of Steve acolytes for months while he learned how to be a person again - probably had no fucking idea about the arc reactor. Even if Hydra knew what it was and told him, he's still in no position to stop the one man everyone has been telling him to trust for months.
Steve doesn't just "mess up" sometimes, but hey, he's still a good guy. Steve is just a shitty guy who treats people good when things go his way, and treats them bad when things don't go his way - even to the point of months-long build up of this cycle that's just presented so normally. He's the supposed leader of the team, why shouldn't he do this?
I don't know, maybe because it's abusive.
He was best friends with Howard, after all.
