It is nice idea seeing people taking their time to promote Bitcoin, but I can't really say that the person selling the T-shirt with the Bitcoin logo on it is doing it with that Bitcoin best interests in mind. After all, a logo alone won't help people understand Bitcoin existence because many people view images on clothing and other objects as common thing.Therefore, it is difficult for people to understand information from merely photographs unless they have prior knowledge of the topic, yet some people can still comprehend and request additional information about Bitcoin if they noticed the logo.
Keep in mind that we live in a country where we are not allowed to buy and sell through bitcoin. Therefore he is selling the shirts in the fiat currency however all the shirts have Bitcoin logo over it. This is the maximum he can do to promote bitcoin. I hope when some day bitcoin may become a legal tender here also, then he can do the transactions in Bitcoin.
If that is the case, then I would suggest that using this approach of T-shirt sales to raise awareness is a great idea, but it has to be redesigned so it can add a few little words in such away people can quickly notice the existence and found way to do their own research.Although the existence of Bitcoin is nothing new, raising awareness of it can only help it receive greater attention.