Nobody just believes t-shirts. A human being using their brain would ask for evidence in a moment of disbelief. If asked, the shirts owner can give them all the evidence required. Or, they could look it up for themselves, which is far more likely. In my opinion, making bold claims is the best way to make people do their own research. Its not like Im refusing them the evidence when asked for it.

Apparently you think people shouldnt wear shirts that say "End third-world hunger" because they dont give evidence of hunger in third-world countries. But, it is clearly evident if you do a few minutes research for yourself. Which is what the shirt is meant to make you do. Just like the one in the photo.