No, it's a marketing issue.
Bars can already be found liable for drunk drivers if an investigation proved they kept pouring booze into people who had no business driving.
If a gun seller sells to a person they know is crazy, without doing a proper background check, then they should be held liable when that nut shoots up a theater.
When I got a home loan, I had to provide a ream of documentation even though I had previously gotten three mortgages, all of which I fulfilled. It took 30 days to review all the documents, and the loan processor told me it was quick because I had all my ducks in a row.
When I got my current job, they gave me a piss test, a background check, reviewed my financials, talked to former employers and coworkers, and this was AFTER a current employee who I previously worked with vouched for me.
I am currently in the process of getting my wife legal residency (Even though they've had her asylum claim for the last 7 years, they've done nothing with it.) I've had to submit 200 pages of documentation to prove that this is a legitimate relationship, and not a Green Card wedding.
When I applied for my Illinois FOID card (you know, where we supposedly have tough gun laws), I sent them a picture of myself and $11.00 and filled out a form swearing I wasn't a criminal or had a mental illness. That's it.
Seems that last one has too little scrutiny compared to the other three.