You're full of shit, or a liar, or just plain stupid... maybe all three.
Where did you get the plainly wrong idea that "The whole thread is around the topic of new "better" background checks"? No, NO it's not.
Gosh, do you even read the thread? The post talked about a bill Gabby Gifford is planning on introducing. It hasn't been passed, it hasn't become law, hence it is a hypothetical.
Since you missed it apparently, I used quotation marks to illustrate they claim it to be a better system, not that I actually think it will be a better system. It is a bit of what we call sarcasm.
I didn't say they would have passed a hypothetical background check, dumbass, I said they passed the existing background check, which is exactly the same background check that will be utilized by HR8 if it passes the House, the Senate, and Trump signs it. You think that criminals that now don't submit to background checks in acquiring firearms are suddenly going to do so in honor of their deep respect for Gabby?
Apparently I have to post your own statement for you to read....

You piggy backed on changemyoil's statement that Gabby's bill would not have prevented her from being shot by saying
"Nor any other victim of a "mass public shooting" in the 21st century."
Now I am going to spell this out for you since you seem to have trouble following.
1. You are making a blanket statement about dozens/hundreds of incidences
2. The bill Gabby proposed does not yet exist as law
3. You are making an affirmative statement that this yet to exist law would not have caught a single individual.
Now maybe I am making a foolish assumption, maybe you have researched each mass shooting over the past 19 years, and maybe you tracked each gun and confirmed that none of the guns used in any of these shootings were ever sold to someone who would have failed a background check but I am betting you haven't.