Actually in the present Captain America series the public is actually turning on Cap. He doesn’t have as much political pull as you think he does in the U.S. government. Even when him and Carol went before congress to oppose the law they got rejected. So Storm telling him talk to his lawmakers, well they did and the lawmakers shot them down too. Now going in there to demand to talk to Xavier I’ll give you that was a terrible approach. Though acting like young people, who others view as mutants though it hasn’t been confirmed, isn’t a huge cause for concern due to the optics around said law is a huge international incident waiting to happen and it was urgent that they be given a talking to before it spirals out of control.