All of your analogies diverge from the matter in that they include demonstrable harm to the subject. There is no demonstrable harm to you downloading spam from your mailbox on your ISP's mail server. If anything, it is the ISP who is harmed by the storage, CPU cycles, and bandwidth that is being eaten by the spam they receive. To the user, it is merely an inconvenience, like a commercial on TV or a billboard on the road. It's the ISP's machines that spammers are exploiting for their own gain, not yours. Only when someone compromises your machine directly (such as using a security vulnerability in your mailer to install spyware) can the responsibility be laid in others' hands.

The thing is, you also have a choice to use a ISP who actively polices for spam and spammers. Such an ISP will cost more (since they are not being subsidized by spammers), but the fact that you have a choice in the matter means that the claim that one is "forced" one way or the other is nothing more than whining hyperbole. Face it. Most people actively make a choice to use a bargain-basement ISP, and they get what they pay for in that regard.