It's human nature to lie and human nature to doubt when someone does something unnatural such as not have children
Well people sometimes lie, yes. But it's a very dim view of human nature to make that the default assumption. You might need to do that at work - it's not healthy to do it for the general population.
As to not having children being unnatural, it's hard to know where to begin. Human beings do a huge number of things which are unnatural. In fact when you pause to think about it, large parts of our daily lives are unnatural in comparison to non-human animals.
That said, not reproducing is in some circumstances part of the natural order. If you look at sociable mammals such as meerkats for example, it's common for certain individuals to breed more than others and some not to breed at all. (Look up "cooperative breeding" for more information on this.)
And remember, we are supposedly intelligent animals. We can just work out that not breeding is fine, given how crowded the planet is. Plus, evolution isn't teleological. So it's quite possible for some people naturally to not want children. It can be a part of their nature. We won't die out because of this. (And if you look at some of the thinking on the evolution of the menopause, it is often beneficial to have adults around who aren't fertile because of the benefits they can bring to a group).
So I don't think you have much idea of what constitutes natural or normal behaviour.