Because people are “free” to say and do whatever they want.
Jesus knew Christians would be persecuted because he was persecuted.
“If the world hates you, keep in mind that it hated me first. If you belonged to the world, it would love you as its own. As it is, you do not belong to the world, but I have chosen you out of the world. That is why the world hates you. Remember the words I spoke to you: ‘No servant is greater than his master.’ If they persecuted me, they will persecute you also. If they obeyed my teaching, they will obey yours also. They will treat you this way because of my name, for they do not know the One who sent me. If I had not come and spoken to them, they would not be guilty of sin. Now, however, they have no excuse for their sin. John 14:18-22
If the leader is attacked, the followers will be too. Christianity is hated because of what it asks and the morality it preaches.
However, persecution is America is very small compared to other countries where it is illegal to gather as Christians (China) or illegal to convert someone to Christianity (Turkey, Saudi Arabia, Iran, Iraq, etc.). The rising influence of Islamic Sharia Law is causing more persecution amongst Christians.
Persecution in America may cause you to get overlooked for a job or ridiculed by your neighbors. Maybe you have to eat alone at lunchtime. This is nothing when you think of Christians fed to the lions or used as human torches to light the streets of Rome back in the time of Nero.