@tmwsiy said:

You think DC Comics would be cool with this? Doubt it.
Think they'd win if they took them to court? I would guarantee it.

No difference at all to the Firestone hat.

Don't be so sure. I'm no trademark law expert by any means, but I can spot at least a few relevant differences here. Firestone apparently sells clothing, increasing the likelihood of consumer confusion between the two products. I'm pretty sure that DC comics hasn't opened a line of vacuum cleaner or sewing shops, nor would any consumer think they had.

Second, seems to me there's more similarity between the two Firestone shirts, given that you could legitimately confuse them if you were just looking from afar, which doesn't seem to be the case here.

Basically, the main touchstone (as I understand it) is likelihood of consumer confusion, and there doesn't seem to be much in your example. As I said, trademark isn't my area of law, so I could be wrong about some of this, but the point is that it's a bit more complicated than you're making it out to be.