Re: "Of course people don't always profess to caring about their own fitness. Rather many profess to be altruists." This is a non-sequitur.

Not really. Selfishness and altrusim here merely refer to whether you behave in the interests of your own genes, or whether you engage in self-sacrifice on behalf of others.

The effect I was discussing is illustrated well by my Bill Hamilton quotes:

A world where everyone else has been persuaded to be altruistic is a good one to live in from the point of view of pursuing our own selfish ends. This hypocracy is even more convincing if we don't admit it even in our thoughts - if only on our death beds, so to speak, we change our wills back to favour the carriers of our own genes.

...and...

Definitely on all fronts is has become imperative not to bristle with hostility every time you encounter a stranger. Instead observe him, find out what he might be. Behave to him with politeness, pretending that you like him more than you do - at least while you find out how he might be of use to you. Wash before you go to talk to him so as to conceal your tribal odour and take great care not to let on that you notice his own, foul as it may be. Talk about human brotherhood. In the end don't even just pretend that you like him (he begins to see through that); instead, really like him. It pays.

- http://alife.co.uk/essays/nietzscheanism/