You are overreacting.
You might not realized that China is a VERY large country. Three times the population of Europe and 40 times that of Canada. Problems happen more when you have large country. It's just normal belt-curve: every time you double a population, you get 10% more of good (Olympic golds) and bad stuff (poison food).
That one milk company was unfortunate, but why are you making it sound like the government is conspired to add poison to your food? In fact, they execute people who were responsible. Many Chinese still hates Japanese for the Raping of Nanking, once in a while some terrorists deliberately poison food that are exported to Japan. You don't have to worry about those.
How many times have we had food problems this year? I've lost count. China is 40 times larger. If you are completely fair, China's food supply is far safer.
I'm more concern with the jobs we've lost.
If you really care, buy only locals. If there are enough of you. They wouldn't export the jobs. It's a waste of time to write angry letters to the company because they know you are unwilling to pay more for their American workers.