For example, home made vegetable soup is artificial. It's made by humans, it doesn't occur in nature, so it's artificial. But most people would feel that it is clearly a natural thing. At least, it's made from all natural things, like vegetables, herbs, water, cream etc. so it must be natural. But everything is made from natural things. You can't create or destroy matter (the most you can do is transform it to energy, and you can't create or destroy that either) so the most "artificial" thing you can think of is, at the end of the day, made from something that occurred naturally.
Perhaps you feel I am just arguing about semantics, and I must understand what people mean when they say something is "natural" or "artificial". So for now I'll accept a (fuzzy and ill-defined) meaning of the word "natural". But I still cannot accept that everything natural is good and everything artificial is bad.
Natural things that are good: strawberries, hugs, a baby's laughter
Natural things that are dangerous: belladonna, tigers, arsenic, drowning
Artificial things that are dangerous: guns, methamphetamine, Zyklon B
Artificial things that are good: vegetable soup, living in a house, pacemakers, looking things up on the internet
So we can't find out if something is good or dangerous simply by deciding whether it is natural or artificial. So how do we find out if something is good or dangerous? Use the fact-checking method I recommended in an earlier blog post