Like him, I think asking people to accept the GPL is completely irrelevant to your legal position. Unlike him, I don't particularly mind about being asked to accept the GPL or think it's a big deal.
If I were to offer an opinion, I'd say some of the tension here arose from the use of the word "accept," and it's probably a lawyerly kind of thing - the tendency to get all uptight about specific use of words (Of course, I don't know for sure that he's a lawyer!). He's saying, it's meaningless to use the word "accept" with regard to the GPL. Like a speed limit or something, the GPL doesn't require acceptance. Unlike an EULA, which is an agreement between two parties, which only takes effect if both parties actively "accept" it, the GPL is like a law - it just applies. Someone's refusal to "accept" it is meaningless; there's no way to opt out of it.
But your desire to inform people of the law is completely reasonable. So you could use a word other than "accept," and perhaps that would make Captain Chaos happier even if the checkbox were still there. So if, for example, the user, by checking the checkbox, rather than"accepting" the GPL instead simply acknowledged it, or acknowledged being informed of it, or acknowledged that the redistribution of the program is governed by it, or whatever.
Then again - the way it is now is kind of like saying, you can't get a drivers license unless you check a box "accepting" the speed limits. Sure it's true that that's meaningless in a way, because you can't get out of the speed limits by not "accepting" them. They are the law. But that doesn't mean the state mva might not put such a condition on getting a drivers license - requiring that you actively agree to abide by the law (which is effectively the same as accepting the law - because the same reasoning applies; after all, you are required to abide by the law whether or not you agree to it). And really, it doesn't seem all that unreasonable, being required to agree to abide by the law as a condition of getting a benefit, even if you'd be required to do so anyway if you didn't agree.
So in the end, after working this through, I think that while I agree with Captain Chaos that it doesn't effectively add anything to require people to "accept" the GPL, I also agree with you that it nonetheless isn't unreasonable to impose such acceptance as a condition of using the software. If you had the same issues as he does about associating the word "accept" with distasteful EULAs, or if you really wanted to make him happy, you could phrase it differently and not lose anything thereby (that's where I think he's correct - you don't "need" the accept language; that particular choice of words doesn't add anything to the protection you have). But otherwise, it doesn't strike me as particularly unreasonable - I see no other reason to change it.
Not that my opinion necessarily means anything; that's just the (casual, not binding, not researched
) conclusion I come to after attempting to work through the issues... And I'm sorry to bore you or anyone with this ramble; I know no one really cares that much - I just hated to see this end so acrimoniously.