Well, in addition to the strawman that this argument is (which reformedfan nailed!), it is also a pragmatic argument. Now, ordinarily, we consider pragmatism to be a good thing, but when it comes to an argument, it's bad. Appealing to the practical consequences of an argument as a justification for or against it is irrational. Saying that affirming Calvinism is bad or wrong because it has poor application to real life is no justification for anything. This is a common argument from those who have ultimately conceded that they cannot refute Calvinism's scriptural and logical arguments. They're scraping the barrel, trying to come up with a last-ditch argument, and it's usually this one.
In addition to being completely wrong about Calvinism's applicability, they are wrong to view the argument in light of its practical consequences. I'll give an example.
Let's say that a city is having a problem with theft. We'll imagine it has gone up threefold in the past three years. The city really wants to do something about it, so they ask you what they can do to reduce the theft. Your answer? Immediately shoot all thieves on sight without a trial. Moreover, issue every citizen a firearm and make it a law that all thieves must be shot on sight. If anyone sees a theft in progress and does not shoot the thief, then he too must be shot.
Now, the practical consequences of this situation will undoubtedly be a dramatic if not complete reduction in theft. But does anyone agree that this is a good thing? No, of course not. Although I have reversed the emphasis in this illustration (bad argument, but good consequences, as opposed to good argument, but "bad" consequences), it should serve its purpose in showing why practical consequences are not a valid gauge for an argument.
Soli Deo Gloria
Jon