The methodology of the StackOverlow survey does not prove anything, but your sources aren't any better. I have never in my life searched "[language] tutorial" because I always search something more specific (or I use "getting started" instead). That removes me from PYPL completely.
The methodology is quite different, TIOBE consider Google, Google Blogs, MSN, Yahoo, Baidu, Wikipedia and YouTube.
"The ratings are calculated by counting hits of the most popular search engines"
The difference compared with StackOverflow is obviously, but most probably it is obviously just for me.