It has come to my attention that you have an affinity for trolling, slander, and libel. So your claim that Bernie Sanders is a Stalinist should actually not surprise me.
I have many relatives, friends, acquaintances who have traveled many times to the USSR and to Fidel Castro's Cuba for both professional travel and personal vacation. There is exactly zero percent chance I would expect any of them to give me a speech on the evils of Che Guevara or Lavrentiy Beria upon return. That is not an expectation people have in real life.
Russia, Ukraine, and Cuba are wonderful adventures for any sophisticated person with an interest in world culture. A vacation, a honeymoon, or a professional trip to Russia does not have to be justified to Trump ass-lickers, rightwingers, teabaggers, libelers, slanderers, gossipers, or wingnuts.