Reasons why the capitalist world wants to keep you from reading Stalin:
1) The world communist movement was at its most united during the Stalin era.
2) He was a major theorist who explored the right to self determination of oppressed nationalities.

3) His administration was the first in the history of the world that actively built a socialist country brick by brick. He was insanely popular in the USSR to the point where the people kept naming stuff after him.
4) His popularity tripled after the USSR's costly victory in WW2.

5) The COMINTERN, the international communist organization which was headed by the USSR during the Stalin era, actively gave support, advice, guidance, and material aid to *all* communist parties across the world, such as the Communist Party USA during the Great Depression.

6) Speaking of the Depression, in the segregationist USA, the USSR opened their doors to African Americans who were denied work in the US to assist with socialist construction in the east, guaranteeing them protections against discrimination and access to health and education.

7) Furthermore, while the capitalist world was in shambles due to relying on the free market for private profit, the USSR was achieving rapid industrialization in the span of a few decades, increasing the livelihood and wealth of all due to their planned economy for public needs.

8) He developed the living political ideology of Marxism Leninism, based on the lessons of Marx, Engels, and Lenin, and the experience of the Russian Revolution, which still to this day guides millions of revolutionaries in their struggles against capitalism and imperialism.

9) Marxism Leninism was (is) the ideology which guided revolutionaries in Cuba, Korea, China, Viet Nam, Laos, Mozambique, Grenada, South Africa, Angola, Ghana, much of Eastern Europe, and much more against colonialism, capitalism, imperialism, and fascism.

There's more to be said about him. But in total, the main reasons he's painted as evil, worse than Hitler, and a totalitarian monster was that the example of his leadership in the USSR and his theoretical contributions were a direct threat to the capitalist world.

There's always room for criticism about his history, but I will say for you to actively investigate historical circumstances before you parrot wild, unbelievable lies about someone who has the same enemy as you. Here's a starting point: https://static1.squarespace.com/static/5ed33bcd368e221ec227cacd/t/5ee39a1731781f54f197c5f7/1591974443348/Domenico+Losurdo+-+Stalin.pdf