The headline uses the word “demagogue” to describe Trump. “Demagogue” is defined as:
A political leader who seeks support by appealing to the desires and prejudices of ordinary people rather than by using rational argument.
I think OC is arguing that the article hints that Trump’s campaign is devoid of rational argument by using this word, which would imply that they aren’t exactly on Trump’s side. I’m not personally familiar with the Guardian’s political standpoint, though.