I don't see anything harsh or out of line about the OP's view on this. This isn't about being a "good guy" or demonstrating that you can grin and bear the small stuff. And it's not about expecting a perfect product, either. It's about the expectation that for your money, which here, is plenty, you'll receive what we call a "merchantable" product.
The light leak seems to admittedly be a flaw, correctable or not. With all bigger money DSLR's, the manufacturer of the product needs to know that flaws that are incompatible with the basic object of the product aren't going to be considered small stuff. Likewise, loyalists and people that pride themselves in "not sweating the small stuff" can be mum if they choose to, but they shouldn't be squelching polite commentary about such issues. Trust me, manufacturers need to know that customer satisfaction and loyalty do not go so far as to make flaws or errors off limits to discussion. At the end of the day, if you expect less, you'll get less.
Everyone is entitled to their opinion on both sides.
However to me, this is what I object to:
"Either way, I’m returning mine, and will consider buying it again after Canon has satisfactorily addressed the matter. Shipping a brand-new camera back to Canon to have it modified or repaired is completely unacceptable, and utterly out of the question."
I just think its totally fair to offer a fix and unnecessary to object to it.