When you sign up with an ISP, you enter a contract specifically stating you will NOT engage in any illegal activities, and will indemnify the ISP for any damage they incur because of your illegal activities. Living in a free society does NOT give you the right to break the law.
One of the rights of a free society is privacy, one of the obligations, is you will comply with the law... not always easy to do - or even desirable!
Using the cabbie analogy, watch the movie "Collateral" - the cabbie is dragged into a nightmarish scenario where a hired assassin uses his cab to go around committing murder. As long as the cabbie asks no questions he's safe from being killed himself. Problem is... he gets involved. Was the cabbie right or wrong to try to stop the assassin??
The law has a very definite view, if you assist a criminal in their activities, you are a criminal yourself. What right do you have to make a criminal of someone else? What rights do THEY have to protect themselves and prevent becoming a criminal because of your actions? Whose rights take precedence?? Again, the law is very clear... you have NO right to make another person a criminal, they have EVERY right to prevent being made a criminal.
We won't even get into the moral values of trying to defend the criminal acts in the first place. If a law is bad, change it, don't break it!
Now, the high ground aside... an ISP isn't going to be snooping through your packets trying to trip you up - they simply don't have the time or resources to do that on any sort of scale - nor do they have any incentive. If you break a law and your IP is tracked by the site YOU invaded... they will alert the ISP, verify your activity, and hand you over to the authorities who will prosecute you in accordance with the law.
Just because you're given the freedom to do wrong, doesn't mean you HAVE to 