Dear TS, (specifically Logan)
I believe that if your Stop Buying Apple Products shirt is missing the key focus of what you are trying to achieve. It is easy to see that Apple's mistreatment of the Chinese workforce is an issue that you care about greatly so I hope you'll feel like pursuing something greater.
While the shirt is original and I want to state that I have no issues with it and you should continue to sell it. I think from what you have said it simply isn't enough to help promote this cause. If I wasn't aware of what it is trying to achieve, and out in public seeing someone wearing the shirt I would assume that the person was under Samsung's thumb like some people are to Apple. If I asked them why I should stop buying Apple products, I'd probably get a half-assed rendition of one of your spiels on the matter and assume they were a hippy (My fault that one). So you can see why that selling this shirt simply isn't doing enough. Only a minority of the people subscribed to you have purchased the shirt, and a smaller number again could explain the cause in entirety. This is about as effective as a hose in a housefire.
As of this minute you have 512,102 subscribers with each one of them having more reach into the world. With this more light can be brought onto the issue at hand and has a better chance of doing something significant about it. Whether this is a petition or something else the more people able to get behind it the more that can potentially be done to address the issue and every company causing harm. As you said, there are a lot of people here, even on the forum that can get together and do things (or something along those lines).
This is just my two cents worth, take it with a grain of salt.
Cheers for listening!