They have sided with Grillo, that all the establishment is calling a clown. Both have criticised unqualified free trade, both have spoken against rising inequalities, both have spoken for regulation and higher taxes on the rich. The rich certainly don't consider them mainstream -nor do the freshwaters who claim that no-one thinks like them (apparently not even themselves).

Claiming that whoever does not say exactly what one wants to hear is engaging in careerism and pandering to the establishment is just sectarian behaviour and says more about the claimant than about the accused.

MMT is just one school of thought. It might be right about everything, everyone else might even be wrong (not the same thing -relativity does not make newtonian mechanics wrong for what happens on earth), but even that would be a far cry from concluding that everyone else is intellectually dishonest for career reasons. The burden of proof would be on the claimant, and so far much of the evidence, for those two, points the other way.

Earth provides enough to satisfy every man's need, but not every man's greed. Gandhi