Once you, the user, are removing root certificates from your browser, the trust system has failed. Especially since while you and I may understand the full implications of such an action, "you the user" in general can not. The entire point of the trust system was to remove the need for the generic end-user to make such decisions, and if it fails that, it fails everything.
Moreover, even as a sophisticated user, I have to observe that I actually do not trust a single root certificate in my browser the requisite 100% that is necessary for this whole system to work. I can not assign a 0% probability to any of them being compromised by a hostile force, especially when the hostile force isn't necessary a random hacker but may be a sovereign government.
So, while your point is totally correct, it should be pointed out it isn't really a defense of the current system. (Which you may not have intended it as, but I have seen others use it this way and it's worth pointing out.)
One cannot be 100% sure a CA isn't compromised by a robot coming from the future. You don't have to 100% trust a CA, but you have to know how much trust you'll give to the whole system.
That's not the way in which the system is structured for 100% trust. The problem is that the system as a whole produces a binary answer: "Yes, this site has passed your trust chain" and "No, it has not." There's no room for dodgy certs, and certainly no room for dodgy root CAs.
Further, there's no room for decreasing my trust in a cert based on the length of the chain, or who's on the chain, or anything like that.
The whole system is structured to produce a 100% certification of trust, or a 0% certification of trust. This has the consequence that when the system is compromised in the way that you talk about in your last paragraph, it doesn't degrade; it falls apart.
It's not that robots from the future might compromise a cert, and going to something so fantastic in the light of the real threat of sovereign governments and the proved threat of compromised root CA certs (proved as in "you could buy this device for real money and have it really delivered to you") is a rhetorical unkindness. It is that nobody can any longer claim with a straight face that the system is 100%, and unfortunately, with SSL that leaves only one alternative.
Compare with the semi-mythical "web of trust", which would have ways of dealing with this that doesn't violate the very mathematical foundations of the system.
You can always remove certificates from CAs you don't trust. If you don't trust Verisign, how can you tell Amazon is really Amazon?