Ok, point one: It's a fucking bong people. It is not, in anyway shape or form, a crackpipe. It is clearly, clearly, fucking clear as day a bong. How in the high holy hell are you people not getting that? Seriously, have you never MacGuyvered up a bong in your lives? Or just bought one, or seen one at some point? Subpoint: Ok, let's just assume most of you haven't done any drugs ever (or at least none of the ones you were told were drugs), and have somehow never hung out with someone who openly did; you do know crack and weed don't have anywhere near the same effects, right? You don't need to actually enjoy some recreational chemicals to figure that one out.
Here's a hypothetical for you:
Say some guy who smoked a fair amount of crack in his youth, and had a good few friends that smoked a hell of a lot more, a couple to the point that they would eventually die from related health issues, had a look at this strip.
He might see a very familiar scene, and although he might know the artist meant it to be pot, to him, popping a rock into a pipe made just like that (and a whole variety of similar designs) would the first thing that comes to mind, because he, and a lot of people he's known over the years in a variety of locales, have done just that for far longer than is remotely healthy. Although, to be fair, he might well accept the argument that any time spent sucking down rocks is far longer than is remotely healthy.
So then he might make a wry joke about it. And he would probably be ok with people not understanding and saying "Uh, I think that's meant to be pot, dude", but he also might find it kind of irritating to be directly quoted* by a bunch of internet know it alls and told that "that's clearly not a crack pipe, bongs and crack pipes are absolutely nothing alike", when he knows from years of experience that it's a home made water pipe, for smoking stuff, because other than the need for a load of ash to soak up the crack as it melts/burns (unless you like the tube and gauze method), there's no real difference in the process of burning and inhaling the smoke of either. And in the event that you use a water pipe to smoke crack, it's a crack pipe. Doesn't mean it's not also a bong, doesn't mean that it's not also for smoking weed, hash, meth (he might guess, he's had no experience with meth), cockroaches or whatever else you want.
This hypothetical dude might also question how this comic shows the effects of either drug. She lights up, inhales and breathes out, then makes a comment about brunch.
[Additional:Hopefully this has explained to you why, despite being a bong, commonly used for smoking weed, it is also possible for it to be a crack pipe, commonly used for smoking crack (though admittedly not as common a design as the good old foil/bottle/biro or Martell/pan scourer combinations).] Hypothetically of course.
*yourself would of course not be counted among this number.