Your premise and question set up a false path of responsibility and utterly fails to address the actual person doing harm. I find that effort to shift responsibility quite odd.
It always surprises me how people do not see the weakness of this argument and why it fails to move people. The overwhelming majority of people are not blinded enough to blame the gun for suicides, as they know the trigger must be pulled by a human.
Thus, the overwhelming majority are naturally not going to blame the gun store for a person using a gun to harm himself. They naturally feel sorry that someone felt that need and feel sorry the person did not get help prior. For the overwhelming majority, it is rightfully not the method, but the mindset that they realize is the cause of suicide.
A few analogous thoughts about this shifting of responsibility to the gun store that illustrate why this approach falls on deaf ears:
The gun store has the same responsibility as a car dealer to verify the person buying a car is not an alcoholic and a drunk driver about to kill people since drunk drivers kill 10,000+ people per year. Why not the call for car dealers to ensure they sell only to sober people and hold them responsible if they sell to an alcoholic?
The gun store has the same responsibility as a pharmacy to ensure the pills bought are not being stockpiled and going to be used in the future for an intentional overdose. Why not the call for pharmacies to be liable (even if proper prescriptions are used) for selling too many drugs to the same person or families and holding them responsible for selling to an openly suicidal person, proper doctors’ prescriptions be damned?
The gun store has the same responsibility as bridge designers and builders to ensure that people cannot jump off their bridges. Why not the call for bridge designers and builders to be liable for making sure their bridges cannot be used as a jumping off point for surely they could design jump-proof bridges?
The gun store has the same responsibility as car designers and builders have for people who die in accidents caused by speeding. All my cars can go anywhere from 2.4 to 4X the 55 limit, and 2 to 3X the 75 highway limit. Why not the call to hold car makers for designing and building cars that can go faster than any posted speed limit for obviously it is misuse of the product to go faster than legal? Specifically, why not the call to hold them liable for making the car able to go faster than the rated limit of the car’s safety features?
The gun store has the same responsibility as any beer or alcohol maker has for college students (and others) who get drunk and then claim sexual assault when intoxicated. Why not the call to hold beer and alcohol makers liable for selling a product that when used properly, i.e., ingested, causes a person to be openly less able to fend off sexual assault?
Overall, gun control advocates need to make their arguments more cohesive, as they are all over the place in terms of responsibility shifting.
There is the call for more in-depth background checks and the like (which I think everyone agrees on in principle), and then gun control advocates say that the federal government should run it, just like the feds do now. I think I can make this generalization about all posters on this thread - better background checks.
However, then in the same breath, some, not all, want to blame the gun store for not checking more thoroughly. Huh? Gun stores are not in control of the background checking process, never have been, so why the heck blame them? Do you think gun store owners are mind readers and who can sniff out suicidal people even if a government background check says they are OK to purchase? Best blame your federal government which runs the background system and your congressmen who ignore your calls for more intrusive mental health checks - but then also expect the ACLU with civil liberties and HIPAA issues.
Gun stores are legal businesses selling a legal product that is heavily regulated by the federal government, just like car, drug, and alcohol producers. Yet some advocates what to blame the gun owners specifically for following the laws of selling a legal product. It is not as if gun stores are lying to consumers and saying guns, if fired at people, do not kill.
Everyone knows a bullet can stop / kill a human or other animal - that is the whole darn point of the thing!!! When hunting, a gun is effective and efficient in helping gather food. And when being attacked, it is an effective and efficient self-defense tool precisely because it can stop a human attacker - no good if it could not effectively stop an attacker. Therefore, since this use and ability to harm to the point of stopping something or someone are understood, it is up to the human purchasing the gun to be responsible with his legal product, not the gun store.
This thread really illustrates why the call of more gun control has gone literally nowhere - the main arguments fall apart on logic alone and thus most people, who not being reflexive based on just not liking guns, are not convinced at all.