I've already thought of this quite a bit and reached a conclusion, that I like to call "the gulag museum problem".
As a communist myself: many people were brought unjustly to prisons in the hardest years of the USSR and suffered greatly there, probably hundreds of thousands of innocents. Should there be a museum dedicated to them? Yes.
However, this is focusing on one event in one particular difficult time of history in one particular socialist country. If we start counting the victims of capitalism and colonialism, and compare to communism, we will reach astonishing numbers. The problem is therefore not the existence of the gulag museum: the problem is that for every gulag museum, there should be 20 museums about the victims of capitalism/imperialism/colonialism.