"On the contrary, Johnson is prepared to stand up for all kinds of things, so long as they are popular, whether he personally supports them or not."
So what? More power to him if he is prepared to stand up for things irrespective of whether he believes in them or not. In general our representatives should represent us and should be led by what we want rather than them listing their manifestoes and us voting for the one we find most acceptable or least unacceptable.
They need to remember 'we're the public, you're the servant.' 
Disclaimer: I don't really believe that last line but always think that play on words is funny. It's in my head from something I watched which is in a strong Scouse accent (I love the accent).