Steve winced, despite knowing full well that he deserved that tone. He really, really didn't want to throw Peggy under the bus, either, but not telling Bucky about this just wasn't an option. He couldn't claim to have divine knowledge about Zemo without some sort of reliable source. And since Peggy had recently been stuck in the baron's room, it would have been obvious where he was getting this information from regardless.
"Honestly? Not when it comes to Zemo, no. In everything else, in every other regard, yes, absolutely. I trust you completely. But you know I thought Zemo was trying to get into your head, and I definitely don't have a reason to trust Zemo himself." Steve huffed out a sigh and added, "Didn't. I didn't have a reason. But maybe I do now. I thought that maybe, Peggy would catch him trying to manipulate you. Or maybe, something would seem off about him whenever he was around you. But as it turns out, that wasn't the case."
Steve's shoulders dropped a little. "I'm sorry, Bucky. I am, I'm sorry. I was so convinced that Zemo couldn't possibly have changed, I didn't want to listen to you. I needed to hear it from someone else that he had. It.. it was never a question of whether or not you were keeping your word, Bucky. It was my doubt in Zemo's conduct that led me to do that."