Christians need to remember and model those early Christians who refused to be silenced, even to the point of death. The verses in Acts that immediately follow Gamaliel's advice not to kill the Christians are more instructive for us, and I argue that the only reasonable discourse is that which is fully truthful without compromise, even if it is countercultural. Especially if it is countercultural.
"And calling in the apostles, after they had scourged them, they charged them that they should not speak at all in the name of Jesus. And they dismissed them. And they indeed went from the presence of the council, rejoicing that they were accounted worthy to suffer reproach for the name of Jesus. And every day they ceased not, in the temple and from house to house, to teach and preach Christ Jesus." (Acts 5:40-42)