Because that is the only point that is actually going on.
This "afterwards nominating nonsense of people nominating themselves" is not the point or the problem in the slightest. Nor the solution.
That's like arguing what kind of flowers to put on the graves of the victims of WW2. Let's put all this shallow ego tripping aside and get to the point.
"Having diversity on the nominating committee is all well and fine, but if the movies aren't there, then there is nothing to nominate.
That should, and is, the only argument."
Exactly.
Go complain to minority people that they should make more babies to take over the world, go write letters to scriptwriters, producers and movie studio's that you like to see more of your minority in films, go protesting on the street, do whatever you feel you need to do, but don't try pulling on something after it's done please.
"Being sure that every person in the committee will always discrimitate and always pick their own characteristics, and basically already accusing the new diverse body of voters of racism and discrimination too" is all fine and good, but that will not lead to more opportunities and it will surely not decrease the gap in race or minority difference and overall view and the origin and solution of the problem. At all. If anything, it leads to forced nominees from a very small minority pool. A mandatory gay award or a mandatory black award. Is that the way to go? Long live the separations.