For real, they seem to forget that the revolution happened in Cuba, against Cuban bourgeoisie.

The sentiment is right, but we need to retire the "Cuban slave owner" meme.

The problem, of course, is that there were no slave owners in 20th-century Cuba. Think about when you weren't as far left as you are now, and you read about something horrible the U.S. did. You probably looked it up, and sure enough the U.S. actually did that. This enhanced the credibility of the source and made you less skeptical of the leftist positions you hadn't already adopted. But this works in reverse when you have an obvious falsehood like "there were slave owners in 1950s Cuba." That shit drives some people away, or makes them skeptical of everything else they read from leftist sources.

And there's no reason to lie about pre-Revolution Cuba, because it was horrible even without slavery. A good source on this is JFK, who (before he became the most open-minded president ever) was certainly no friend to Cuba:

In 1953 the average Cuban family had an income of $6.00 a week. Fifteen to twenty per cent of the labor force was chronically unemployed.

Only a third of the homes in the island even had running water, and in the years which preceded the Castro revolution this abysmal standard of living was driven till lower as population expansion out-distanced economic growth...

But instead of holding out a helping hand of friendship to the desperate people of Cuba, nearly all our aid was in the form of weapons assistance - assistance, which merely strengthened the Batista dictatorship - assistance which completely failed to advance the economic welfare of the Cuban people...

Secondly, in a manner certain to antagonize the Cuban people, we used the influence of our Government to advance the interests of and increase the profits of the private American companies, which dominated the island's economy. At the beginning of 1959 United States companies owned about 40 percent of the Cuban sugar lands - almost all the cattle ranches - 90 percent of the mines and mineral concessions - 80 percent of the utilities - and practically all the oil industry - and supplied two-thirds of Cuba's imports...

The third, and perhaps most disastrous of our failures, was the decision to give stature and support to one of the most bloody and repressive dictatorships in the long history of Latin American repression. Fulgencio Batista murdered 20,000 Cubans in seven years - a greater proportion of the Cuban population than the proportion of Americans who died in both World Wars, and he turned Democratic Cuba into a complete police state - destroying every individual liberty...

[U.S.] Administration spokesmen publicly praised Batista - hailed him as a staunch ally and a good friend - at a time when Batista was murdering thousands, destroying the last vestiges of freedom, and stealing hundreds of millions of dollars from the Cuban people, and we failed to press for free elections.

That's from a staunch anti-communist who would go on to invade Cuba -- even he couldn't paint pre-Revolution Cuba in a better light than this. There's no reason at all to make up shit about slaves when even a cursory look at the Batista dictatorship shows how horrific it was.