LOL!

As long as you avoid those wackos that hide in the bushes and jump out and stab at your tires with safety pins, you should be fine.

That's about what to expect from a tire liner. You're not trying to protect from giant safety pins sticking straight up in the road as much as you're adding protection from all the little things that CAN'T penetrate that thing. Like those little metal pieces of car tires, little rocks, little pieces of glass, etc. The liners definitely help with that stuff.

The tires that came on your Denali are pretty cheap though, and they aren't going to have any flat protection built-in. I'd think about replacing them with something more robust if I was going to commute on that bike. You can get tires with a kevlar layer around the bottom that acts as a built-in tire liner. With a tire like that AND a tire liner, you're pretty much set. (Maxxis Re-Fuse is one example)

Besides the Slime liners from walmart, you can also try to find "Mr Tuffy's" liners from your bike shop or the internet. I believe they are a little beefier than the picture you posted, but you could still shove a pin through them.