2 is indeed dependent on 1. There is no indication that 1 is dependent on 2, however.
The first alludes to a desire to rule, not the reality of rule. And even then, it's hedged with "usually".
Well, yes. It is most commonly used. Because words have meaning.
So if someone asks "Can black people be racist?" and I didn't know what the word meant, I would first look up racism ("a person who believes in racism, the doctrine that a certain human race is superior to any or all others") then I would look up racism, since that's where it points me. I would read the first one and think "I've heard of some black people believing that "inherent differences among the various human races determine cultural or individual achievement" and whether or not it has to do with "usually involving the idea that one's own race is superior and has the right to rule others" doesn't really matter.
That'd be enough on its own to answer "Yes, black people can be racist" but continuing on I'd probably find (in the US) that the second definition probably doesn't apply (although there are some cases where it conceivably could). Then I'd read the third definition, see that it applied, and it would be very clear. The only way someone can say that black people can't be racist is if they restrict the definition of the word for whatever reason, something you've already said is "nonsense".
This isn't really even a debate, although ecofarm's attempt certainly made for some great fun.