Anthropogenic Global Warming
On the one hand, people who say "man-made global warming is a fact" are really not too savvy on the nature of scientific theories. On the other hand, with consensus amongst climate scientists running at about 98% that AGW is real, I don't see how a lay person can do other than operate on the assumption that it is so. Of course scientific consensus is wrong on occasion. But as lay people, you and I are in no position to judge when this may be so. Unless you are willing to devote several years of full-time study to this topic, you just aren't going to understand the literature and the issues the way the pros do; no, in a field in which one is not an expert, and in which there is an overwhelming expert consensus, to differ from that consensus is sheer stubbornness or wishful thinking.