I guess I was only thinking about deliberate or man made genetic selection, not the stuff that's been going on naturally.
With the random example of haemophilia, in the same way as with the original fish growing legs, we may not realise it as a useful trait yet. To a fish in the water legs would have appeared to be a disability and a hinderance. That is why I think it could be dangerous to eradicate genes. If nature tries to adjust, as it does, and we overcome any such adjustment by this type of eradication, we may be halting progress instead of aiding it.
Just because man has no natural preditors does not mean that nature may not be getting us ready for another climate or stage, or anthing else that requires fundamental natural selection. The interim stages of developement could look like nature's mistakes, but how would we know.
I also agree that gene culling is a lot nicer than culling after birth, but something being nicer than something quite abhorant isn't a good argument for doing it. It might just be an argument for not doing the former.
So saying I am probably taking absolute rubbish, it's late and I've been drinking and I think I could probably fit everything I know about genetics on to the back of a postage stamp... twice.
