Conclusion: people are stupid and easily led.
(which is pretty much the fundamental problem with democracy)
Easily led? Yes. Stupid? Partly, though I think you’re being a bit harsh. As you point out the media get in the way of any discussion of policies, so one day it’s big business avoiding tax, the next its pasty tax, but there’s very rarely any attempt to have an informative discussion on e.g. overall tax policies in general weighing up the pros/cons.
As a result “public opinion” actually means “media owners/editors opinion”.