How many times do I have to say this? "People will always find a way to buy guns" is an invalid argument against gun laws, which exist to reduce access, not eliminate it.
A good answer to that fallacy is to ask, "Why don't you get rid of the locks on your doors and windows then? Burglars can still find a way to get in."
My personal pet peeve is the tired "Why don't we ban (cars, knives, spoons, etc.) because THOSE kill people too." That's kind of like saying that we should stop trying to cure cancer because people will still die of heart disease.
If said gun nut is conservative, try: "People will always have sex, why ban abortion?"
--Nicholas Kristof, NY Times
People will always find ways to hurt each other, so we shouldn't have laws prohibiting anything. Is that really your argument, gun nuts?
For example, people will always find ways to kill each other. So why try to limit guns, bombs, flame-throwers, tanks, etc.? Heck, why try to limit murder? It's gonna happen anyway, so what's the point of passing laws against it? Laws only take power from individuals and communities and give it to government bureaucrats.
If terrorists want to kill somebody, they'll find a way. A plane, a bomb, a chemical or biological weapon. Therefore, let's do nothing.
This is the "thinking" of stupid gun nuts.
For more on gun control, see Newtown Shootings Show America's Pathology and Time to Talk About Guns.