I have been asked for an opinion on the above poll, showing "90% of Americans support background checks," and how I would respond to people who cite it. It also asks what people think of armed guards in school, and how effective they think it would be.

The question shown is simplistic and without context, and is a straw man.

Would it matter? 90% of Americans used to support slavery. 90% used to support bans on "pornography" that included the Kama Sutra. It's nice that they have a poll. I have a Constitution. ;)

And what untrained amateurs think of security protocols is uninteresting to me.

Also, there ARE background checks at gun shows, so the question is irrelevant. EXACTLY THE SAME LAWS apply at a gun show as apply outside a gun show. There is no such thing as a "gun show loophole." Just because a dealer sets up at an event hall, doesn't exempt him from NICS checks and Forms 4473, anymore than it exempts him from sales tax.

Speaking of which, when are we closing the "garage sale loophole" that lets people sell things without paying sales or income tax? (Trick question. Technically, you're supposed to collect and pay sales tax on garage sales in most states, and you are certainly required to either pay income tax or file to show depreciation of the used goods.) See how this works? Lie that something happens, claim said imaginary happening is a loophole, call for changes "for the chiiiiiildren!" Take a poll. Pretend it matters.

Yes, a private citizen, NOT ENGAGED IN BUSINESS can sell personal property, even a gun, without a license. This has ALWAYS been true. If you change that, then you cannot complain if at some point they start requiring official drive searches for kiddie porn before selling personal computers, or actually send agents around to collect sales tax from your garage sale. Or, they may start raiding and shutting down farms for selling "unlicensed milk." (Does that sound familar? Because it happens.) If you give the government power, they are going to take it. Once they have it, you can't complain about it, because you gave it to them.

I have made such sales myself, btw. Usually of antique Spanish or Smith & Wesson revolvers from my collection, usually logged into a book and logged back out, since I have a license to collect (which offers me some specific benefits as far as shipping and receiving).

But any FFL selling guns must do a NICS check on EVERY sale, no matter where it takes place, and there are already strict legal limits on WHERE they can conduct said sales (for example, they must be within state). And no wholesaler or manufacturer will sell to anyone who does not have an FFL, because legally they can't. That FFL is necessary to get inventory.

There is simply no possible way to operate a gun business without licenses and NICS checks without running afoul of the law, and rapidly getting noticed.

And by the way, there are ATF agents at most gun shows. Some of them are shopping for personal or duty weapons. Some are resolving legal inquiries from dealers. And some are acting in capacity as enforcement. 

As far as "guns sold on the internet," they either must go through an FFL, or be sold face to face, if private, much like they were when such ads were placed in newspapers. So the question here is: Why do you hate the internet?  Why do you hate modern communication?

Can someone make a sale to someone illicit anyway? Yes. You know what we call those people?  Criminals. And guess what?  THEY DID THAT ANYWAY, and will do it anyway. That's what it means to be a criminal.

But when they drag your ass away for selling or possessing unlicensed milk that wasn't properly pasteurized, etc, "for the children," don't expect any sympathy.  When they jail you for tax evasion over the "Garage sale loophole," no sympathy.  It's what you voted for and wanted.  

Nor can you ever complain about TSA, who checks travelers to "keep us safe" and "protect the children."  If it prevents just one bomb, won't it be worth it?

And next time, try having a clue what you're talking about before engaging in debate.