[Steve stops with her, explaining the situation calmly.] They were dirty from the start. SHIELD recruited former members of HYDRA during its early days for their strategic value. The War ending didn't change who they were and they've spent the past few decades recruiting through SHIELD so they could finish what Schmidt started; what I sacrificed myself to stop the first time.
[He's heard people at SHIELD talk about Pepper. He knows she's well aware of everything Tony has been given access to and that includes his final mission against HYDRA. She has to know about his plans to bomb America to kingdom come. Millions would have died. What would that plan have looked like decades later? Steve's certain she can imagine it.]
They used technology Stark gave them to make it harder for anyone to sink their weapons of mass destruction this time. We still managed to pull it off. Natasha dumped everything they had onto the internet so they couldn't spin their way out of it too. They're done for now.