This rhetoric adds nothing of subtance to the political understanding of either contemporary Trumpism or the history of Stalinism. Sanders only serves to obscure the meaning of this critically important understanding. Fascism and Stalinism are not the same.
To be clear, Stalinism took hold in the Soviet Union as a result of its historic backwardness and international isolation. The failure of the revolution to take root in Europe (largely a result of the historic betrayal of Social Democracy in the Second International) created conditions for the consolidation of a nationalist clique and a bureaucratic degeneration of the workers state that formed from the victory of the October Revolution. That is Stalinism. This political form was responsible for mass murder of the old cadres of the revolution who opposed it, systematic betrayal of the workers movement internationally, collaboration with imperialism allowing for the restabilization of capitalism during its repeated periods of crisis, and ultimately the destruction of Soviet Union union and the restoration of capitalism in 1991. A detailed and correct historical understanding of this history is critically important for the working class as it enters into a new period of revolutionary struggle.
Sanders use of the term as a political slur wrongly directed at Trump confuses the issue, and ultimately gives capitalism a pass for its own crisis. Trump is not simply an evil individual responsible for wrecking America. He is the product of the terminal crisis of capitalism at the center of world imperialism. He represents a financial oligarchy whose wealth and influence has grown increasingly disconnected from social development and the process of production. The historic content of Trumpism has a stronger relationship to the fascism of Mussolini and Hitler than the national labor bureaucraticism of Stalin.
This is no small error by Sanders. This is a deliberate falsification that is calculated to confuse political consciousness and hinder the development of revolutionary conclusions. It should be clear to anyone who takes more than a second to think about it that the comparison to Stalinism is shallow. The historic content of Trumpism is its own.