The baptism into Christ's death also meant the end of our not-so-good status according to law. But that doesn't mean that the law itself is bad. In fact, Paul talks about how he knows what sin is through the law (7:7).
However, Paul talks about how in response to law, sin “produced in [him] all manner of evil desire” (7:8). After all, many of us break rules because of inclinations -- especially since breaking rules is a fairly common temptation. After all, one of the side effects of sin is death. The law reveals the internal problems (though sin takes advantage of it). In the end, even Paul talked about how "sin [...] deceived [him]" (7:11), indicating that even Paul succumbed to motives to do not-so-good actions (just like the rest of us). When Paul talked about how everyone screwed up (back in Romans 3:23), he really meant "everyone" since that included himself.
Paul concludes by talking about how "the law is holy" and how "the commandment [is] holy and just and good" (7:12). It's not the law that gets people to do evil; it's the temptation of sin. But the struggle of doing good in the face of tempting evil is a big one that even Paul himself faces!