As far as I know, Gun silencer doesn't make the gun totally silent it just decreases the gunshot sound. I saw a lot of videos where they try using a silencer but still I can here the sound of the gun shot but its not too loud anymore. For me I think it works, It uses by those police to keep the enemies unalarmed. Try watching some videos where they uses silencer so you can find out if it really works.
If you buy a gun, it means you are supporting those illegal gun makers. It is very risky to buy a second hand gun or a licensed gun because you don't know the history of that gun, it is possible that the second hand gun that you can buy in public is used in a crime and if that gun is tracked by the police you can be in prison because you will be already judged as the primary suspect, they will question you if that gun belongs to you and if you say that you just buy it maybe they will not believe in you. Because a police mindset is that "A suspect will never admit the crime that they've done.
America should ban all of type of gun for me. Because no matter what kind of gun it is. It still a direct threat to all of us who are living in this beautiful world. So for me, the world should ban all kinds of guns.