I use the internet to put in practice what I am learning about critical thinking and argumentation (critical thinking course on Khan Academy).

I understand that meatspace doesn't frequently offers opportunities to test skills like that, but when looking for those opportunities online you should be very picky on where to look. Avoid newspaper sites and (most) blog comments. You need to find environments in which disagreement is a way to find the truth and where changing your mind is encouraged. These are pretty rare. Although if you want to practice argumentation, you might want to check out /r/changemyview on reddit