So if a brand name is old, then it should never be questioned?
Regarding the OP, yes. A corporation certainly should review its brand strategy annually, but in regards to whether using a Rebel should make the consumer feel inferior, that brand has been around 24 years across 25 or more different models, the answer is not to question the name, but whether the model satisfies your needs, and you are able to use it as a tool to capture what you want.
Besides, why any issue with the term? Everyone is a rebel in regards to something in their lives as compared to others. It is not a negative term, and even in today's of silly political correctness, it just isn't something that should raise an eyebrow. If it does, then people need more (and better) things to fill their time on this earth.
In any case in regards to Marvin (TS), based on the pictures I have seen him post, he has nothing to feel bad about using his T3i, his results are quite good.