There are two sides to this argument, and they're both full of shit.
No "other manufacturers" are held liable when someone kills someone else with their product - but no "other manufacturers" seem to need specific laws giving them immunity, either.
The reason for that is self evident. The progressives have tried everything they can think of to ban them. So, they tried this. The law was passed so that they wouldn't waste more taxpayer dollars on ridiculous lawsuits.