Why does Steven hate communism so much?

First of all, I'm not sure where you ever got the impression that Spielberg "hates" Communism, unless you've got a specific quote where has said as much.

Spielberg has only ever made statements condemning murderous fascism (particularly Nazism), and -- him being a Hollywood liberal -- he has actually been pretty soft on Communism. Spielberg even had a friendly meeting with Fidel Castro sometime in the early 2000's, and was criticized heavily for it by Robert Duvall. And by the way: Castro is a fan of Jaws (Much to Spielberg's delight, Castro interprets Jaws from a Marxist point of view because it's a movie about capitalists who allow citizens to be slaughtered in order to protect their investments).

Yes, Spielberg has directed films, such as Bridge of Spies and Indiana Jones and the Kingdom of the Crystal Skull, which are told from an anti-Communist point of view. That doesn't mean that Spielberg "hates" communism, just that he sees it as convenient from a storytelling perspective. He cheerfully said in interviews that "the Russians got the job" as the villains in Crystal Skull because, hey, it's set during the Cold War, and the Russians -- whether you like it or not -- were our enemies back then, so of course it makes sense for them to be the bad guys in an action adventure set during the 50's. At least Spielberg doesn't demonize them; they're there merely to function as annoying obstacles who get in Indy's way.

As for Bridge of Spies... have you even seen it yet? I feel it's pointless to go into large details as to how respectful this movie is of the Russians during the Cold War -- because if you've seen the movie, you'd already know that it is. The film is not criticizing Communism, but the very kind of dictatorship you mention in your original post which allowed the Iron Curtain to take shape, and East Germans to be shot on sight by guards if they tried to flee to the other side. At any rate, the film also goes to pains to suggest that Americans were almost just as ruthless as the Russians were back then, because like them, we also were bloodthirsty, we also cruelly interrogated our prisoners of war, and we also resorted to one-sided propaganda.

And yet, the film finally stresses a profound message of peace. Donovan and Abel -- the democratic lawyer and the Communist spy -- become good friends at the end of the film, thus showing us that even our enemies are still human beings just like us, and that there are ways to settle our conflicts which are alternative to mindless war.

So, I could go on and on debunking this claim of yours that Spielberg "hates" Communism, when, to my knowledge, he's never said anything of the sort.

Of course, I also can't help but wonder why you defend Communism at all. Communism does not permit free speech, and it does not allow people to have entrepreneurial opportunities. These days, Communism is a dying concept because countries all around the world are starting to realize how unrealistic it is. The things which Karl Marx talked about -- complete equality -- are not possible because there's always going to be a dictator somewhere who has to violently keep everyone in line in order to make that kind of equality possible. And -- contrary to what Communism is supposed to achieve (complete equality) -- that single dictator will always profit from the system, while everyone else below him suffers.

I think you'd be better off championing socialism (look at how much support Bernie Sanders has gotten in America, despite fears that he probably won't win the nomination) than you would be championing Communism.

I am very impressed that you replied in such polite, knowledgeable and well-though manner, usually I am showered with insults right from the beginning. Yes, you did point out my main concerns, the movies "Indiana Jones 4" and "Bridge of spies". There are some inconsistencies with the latter, like the fact that the protagonist didn't actually see people getting shot.
I agree that my assumption about Spielberg may be wrong, but I just can't shake the feeling.
Furthermore, I am not defending communism, nor do I believe that it is the perfect good social system. However, I lived the first ten years of my life in a socialist country, so it hurts my feelings whenever western movies show us in negative light.
Overall, I agree with you and accept your arguments. It's a rare thing to see someone behave like that on the Internet, for which I am thankful.

It's a rare thing to see someone behave like that on the Internet

Agreed.

There are some inconsistencies with the latter, like the fact that the protagonist didn't actually see people getting shot.

Well, even if the real Donovan may not have seen people get shot fleeing East Germany (though I wasn't aware he never did; I would need to check up on this), it works in the context of the movie because it demonstrates how much more dangerous it was in East Germany compared to the West side. In real life, anyone who walked up to the wall on the East side really did get shot, whereas on the West side, people were free to walk up to the wall -- and many on that side even got away with spraying graffiti on it. In the context of the movie, it at least shows us what Donovan is escaping once he is hurried away on the train back to the West. Yet he makes the decision to go back to the East side anyway, for the sake of all the prisoners.