It's the broken sob that finally breaks Steve's calm resolve. He's moving when Viatorus turns away, pulling the smaller man into an embrace and doing his best to gather V up and convey as much safety and comfort as he can.

"I know. I know you're scared. But Isidor would never suggest something that would hurt you or be in your worst interest. You know that. Hell, I know that. And I'll be here. I'll stay with you if you need me to. Whatever you need, whatever will help if I can give it it's yours."

There's nothing Steve Rogers wouldn't do for his friends. Viatorus is one of the closest ones Steve has so it only reinforces Steve's determination to support the other.