There is no right or wrong in this. If we applied the logic of "no one other than GM can make parts for GM cars" then most of us would be up in arms about being stung for GM brand brake pads, when the EBC ones are half the price and better. The fact that other companies can produce parts increases the competition and forces Stihl or GM to innovate and become smarter.
The reality is that, just like Japan, China will eventually produce parts that are as good, if not better than the originals. Look at Honda GX engines - I'd take them over a B&S or Kohler any day, but 20 years ago, Japanese stuff was poor quality and cheap.
Where I draw the line is the blatant attempts to pass off products as originating from the original manufacturer. Right now, their quality is also far too variable and generally poor, so I don't buy Chinese stuff if I can possibly help it. What they will find is that by starting to embrace more western styles of employment (which cost more), their quality will rise, but so will the price. They won't be cheap rubbish anymore, they will be mid priced quality.