One thing to keep in mind here is the fact that even if Firestone might ultimately lose here, it's expensive to litigate these issues, especially if you bring in complicated defenses like parody, etc. The question for this Waldo guy is whether it's worth it to spend the time and money just to sell some t-shirts (obviously depends on just how much he's actually making from this little enterprise). Obviously, he's shown he's willing to fight before, and perhaps principle comes into play a bit here, but this is ultimately going to have to be a business decision for him.