Whether or not it is a new being is not the argument. Regardless, the originality of it's genetic composite does not affect the argument you're making.
I agree that originality doesn't matter, however the completeness of the genetic information does. As long as the information is incomplete (in the case of the sperm, half the composite is missing) it doesn't have the capability to develop into an adult human being.
For it to gain the capability, the sperm needs to fuse with the unfertilized egg or in the case of cloning, you need to fuse the nucleus of the person with an egg that has no nucleus. Keep in mind, cloning changes nothing about how we perceive the beginning of an individual's life - it just shows that there is more than one way to get there, as in there is more than one way to create a zygote.
Once the genetic information is complete, then the being will develop into an adult human. The mechanics behind the zygote developing into an infant and the said infant into an adult are completely the same. The only thing that separates them is the amount of time it takes. Any cut-off point in the middle of that development is arbitrary and casually selected.
Unsupported opinion based on the assumption that a fetus is entitled and bestowed rights, when it is in no way sovereign, or able to act on the responsibilities that said rights bear.
If the fetus is a human being, then clearly it is a subject of human rights. I don't know how you define human rights, but the general theory behind it is that you don't have to do anything to have human rights. You have them by virtue of simply being human, you have them by simply existing. Nobody can give these rights to you and nobody can take them from you. These rights can only be violated.
The fact that it isn't sovereign or the ability to act on the responsibilites doesn't have any bearing on the status of the being nor the ability to bear those rights. Children, babies especially also aren't sovereign and they have no concept of rights whatsoever. Yet still, we consider them human and we still consider them to have a right to life.
If the quality of being sovereign/the ability to act on the responsibilities that rights bear is the criteria to determine, whether the subject has rights - then you now have a lot of people that have no rights and can simply be killed off. From children, to the demented/insane to the comatose etc.