Yes, that's all very well and good.

However, in the real world, if your ISP gets a flood of spam complaints that get traced back to your IP, they will shut off your connection. If you've got a nice expensive T1 or something, you'll probably get a few warnings first, but if it continues they eventually have to take action to avoid getting blacklisted in one of the spam databases. You can tell them all about how you're standing up for the principle of anonymity by opening up your WiFi node to the world, but I can guarantee you they won't give a shit.

Similarly, if someone connects to your node and tries to hack the White House's website, the cops are going to show up on your door, confiscate your computer equipment as "evidence", and probably arrest you.

If you still want to open up your node to the world, then great, go for it. But realize that there are risks involved, and it doesn't do you any good to pretend those risks don't exist or don't affect you.