The conflicting information is one issue, certainly. The other is that I think people have a tendency to overlook that there is a difference between gross contribution and net contribution. The gross effect of human carbon emissions is relatively small compared to natural sources -- the equivalent of roughly 1 part in 20, I believe -- and so it's easy to dupe yourself into thinking "so bloody what then?" But the net effect is a lot larger, because a great deal of greenhouse gas emissions are reabsorbed already, so that the excess due to human activity ends up contributing at a far greater rate than the headline figure of 4% or so.
The "gross vs. net" thing shouldn't be too hard to appreciate. As to "climate change has always been happening". Well, duh. This is not a recent revelation and, believe it or not, scientists have kind of noticed this. Just as there is gross v. net, though, there is also signal vs. background. It's a basic principle of data analysis and, again, is probably being overlooked by the sceptics.