They see the result of the gun violence in person, they don’t see the other side. Their view is skewed and while being valid, should be taken with a grain of salt.
If humans weren’t so flawed their wouldn’t be a need for guns.
However if you remove the guns you will still have the flawed humans who will continue to find a way to conduct mayhem.
They often don’t admit any difference between criminal homicide and justifiable homicide, so they lump the two together into one number and say the number is too big. But, doing that is literally amoral, equating a murderer’s action with a defensive response that kills the murderer.