It is content censorship, also known as moderation.
Your comment is overgeneralizing and dehumanizing entire groups. Jews and black people are individuals. They do not have some kind of cultural dogma or collective groupthink. So no, I don't know what you mean, and it sounds an awful lot like you're implying one or both groups are bigoted towards each other.
And even if there's historical examples you can point to, they aren't representative of current individuals.
Even looking at the context, just glibly throwing out, "Well, you know how Jews and black people are," does not look good.
No, because it's still generalizing. This is what your original comment would be if it was modified:
Well you know how the american whites feel about African Americans haha So much rich history there
While the "history there" is obvious, how "the american whites" feel about black people is vastly different from the past. It's true that some people refuse to let go of the past, but most live in the present and will have a variety of opinions ranging from indifference to deep-seated love and support.
The issue is generalizing groups of people. It's a way to dehumanize and "other," and people should recognize it as harmful*.
*Note that there are some notable exceptions, such as Nazis; since the criteria for membership is pretty heinous and membership is voluntary, dehumanizing and othering Nazis is of great benefit to society.