Other things can kill people, kitchen knives, baseball bats, and string, should all of those be banned as well. A company is not responsible for how a buyer uses their product. A gun company should be safe from these just as a kitchen knives company should not be held responsible.
Of course there should be some sort of protection for companies whose products could be used for violence.
However, personal responsibility is not a reliable way of dealing with these issues. People are stupid. People are very stupid. They'll injure people, they'll steal from people, they'll kill people. Somewhere along the line these crimes need to be prevented, and that needs to start with a sense of responsibility from either lawmakers or manufacturers.
Manufacturers will never take responsibility. They don't want to stop selling their product. They'll brainwash and bribe their way into continuing to sell their products, even when the sole purpose of said product is to cause grievous bodily harm.
Frying pans can be used to kill people. A car can be (and very often is) the cause of somebody's death. A gun is made to kill people.
There need to be more laws in place to stop these products getting to the general population.
Manufacturers of guns, or bikes or cars or tennis rackets, cannot be held responsible for how their products are used. A frying pan can be used as a lethal weapon. So could a pen. Bic and Williams-Sonoma aren't responsible for that. When tragedy occurs, it's easy to want to lash out and blame someone, but manufacturers cannot be held liable for what people choose to do with their own free will.
Gun manufacturers are indeed protected from lawsuits over criminal use of their products. It does not make any sense to hold a gun manufacturer liable for the actions of a gun owner, even criminal actions. For example, we do not hold car manufacturers liable for car accidents and deaths which had nothing to do with their product and were 100% caused by human error.
Of course they have to be, if they weren't then they would be absolutely stupid. They wouldn't of lasted this long in the business world if it wasn't for the protections that they have. It doesn't necessarily make it right but it's all about covering yourself and making sure you survive in this business savvy world.
Gun manufacturers should be subject to lawsuits when their products are used to take human lives. They should be actively involved in trying to find a solution to the use of guns, instead of just developing new and more deadly weapons that end up in the wrong hands. Other than military and hunting weapons, gun production should be strictly controlled.