You should take care to notice that this is not a patent, but rather a trademark, which falls under an entirely different set of laws and practices.
In particular, they likely just have a trademark to make shirts with the pi symbol and a period afterwards. While you may disagree that they should not be allowed to have such a trademark, it is the name of their company, and they have to enforce the trademark if they want to keep it. Because this is a trademark, they have to prove that someone else is trying to pass off a product as one of their own in order to take punitive action against the opposing party. What this means in practice is that if someone uses the pi symbol in a paper or on the internet, it's likely not to be confused with the t-shirts they are selling, so therefore there is no trademark infringement. However, if you're selling t-shirts that have a pi symbol on it in a similar fashion, you're opening yourself for litigation. It is also important that they take action against companies that are infringing on their trademark lest they lose the trademark (which also happens to be in their company name).
In any case, this is just a silly story and has nothing at all to do with patents, and nobody should be worried unless you plan on making and selling t-shirts with a pi symbol on the front of them.
Comments
You should take care to notice that this is not a patent, but rather a trademark, which falls under an entirely different set of laws and practices.
In particular, they likely just have a trademark to make shirts with the pi symbol and a period afterwards. While you may disagree that they should not be allowed to have such a trademark, it is the name of their company, and they have to enforce the trademark if they want to keep it. Because this is a trademark, they have to prove that someone else is trying to pass off a product as one of their own in order to take punitive action against the opposing party. What this means in practice is that if someone uses the pi symbol in a paper or on the internet, it's likely not to be confused with the t-shirts they are selling, so therefore there is no trademark infringement. However, if you're selling t-shirts that have a pi symbol on it in a similar fashion, you're opening yourself for litigation. It is also important that they take action against companies that are infringing on their trademark lest they lose the trademark (which also happens to be in their company name).
In any case, this is just a silly story and has nothing at all to do with patents, and nobody should be worried unless you plan on making and selling t-shirts with a pi symbol on the front of them.