In short: You're confusing the term nonsense with Mesmer dislikes. If the word "racism" were nonsense, no one would have a clue what you're talking about.
I'll provide a more thorough deconstruction of the term.
If "racist" meant only people who showed/had racial animosity to others, purely because of their race, I can agree with this sensical usage of "racist". It is intelligible. It is also part of the current "racist" definition that people commonly use. We agree on this.
However, "racist" isn't wholly that definition. It also has a nonsensical part which conflates racial animosity with mere mention of race. For example, when the notion of races having different I.Qs is brought up, as you guessed was in the J.P Rushton and David Suzuki debate, Rushton's research is dismissed out of hand because it is "racist", NOT because it flawed. You could argue that the research is wrong, that Rushton had racial animosity himself, but the arguments he posited themselves cannot be "racist" their function is to find truth (i.e. what are the various I.Qs of human races). THAT's the nonsense -- labelling scientific claims about race as racial animosity. THAT is not intelligible.
Now, just so this distinction is crystal clear, **if** people were to go on and say that well, because Whites have superior I.Q. to African Americans, we should kick African Americans out of America, that is racial animosity as embodies the sensical part of the definition for "racist". If we stop one short of that, if we just say that Whites have superior I.Q. to African Americans, then this doesn't demonstrate racial animosity.
Let's take a different, practical example. Let's say we saw a Jew carrying shopping bags down the street. I see the Jew's knees shaking, the bags wobbling all over the place, and so I say, "That Jew is struggling to carry those bags". Yes, that's not a positive thing to say, but it's what I deem to be the truth. Now, you could turn around and say, "You must hate Jews. You are racist." So, functionally, we've turned a non-positive empirical description into something that is ascribed as having racial animosity which axiomatically cannot be truthful, if we use the term "racist" there. So: perceived truth =/= ever truth, is what we get when we use the term "racist" in that way, which I hope you can see as nonsense.
Again, for clarity, **some** of the definition of "racist" IS intelligible and something I can agree with you on. However, not **all** of the definition is intelligible, and thus this renders the definition nonsense.
Hopefully that is clear now.
I enjoy being taller, but if I were too tall I would have related heart problems. Height is only better relative to some given task; while I am able to lift things off the top shelf more easily than a short person, they can get the bottom more easily; working together with those who are different leads to greater utility.
Within your first sentence, you're already starting to objectivize how tall someone should be: "but if I were too tall...". Clearly, even if only subconsciously, you already agree that certain heights are better than others.
I'm not sure if you're aware of this, but height plays a major role in what people subconsciously think of you, and thus correlates with desirable life outcomes. Height effects your ability: to attract a sexual partner (especially for men), ability to play most sports, ability to move up faster at corporate jobs (only minor correlation to be fair), ability to instantly garner respect of people (for the most part), ability to be seen as a leader etc. Happy to provide sources if need be.
Therefore, I think we can safely say that having more height (to an extent, as you've indicated) is more desirable -- it isn't all subjective.
Simplifying this down on just intelligence: imagine a society made up primarily of copies of the greatest genius: With that staggering intellect, he's unhappily forced to engage in every low intellect trade to keep the society going, thereby making it torture. Of course on this I do not speak of racism, but Rickism.
We know the real world outcomes of top-end intelligences with people like Terence Tao (I.Q. 230), Marilyn Vos Savant (I.Q. 228) and Christopher Hirata (I.Q. 225) who aren't being tortured by boredom, but are instead flourishing in life Here Is The Highest Possible IQ And The People Who Hold The World Record | Science Trends . So, for now, more intelligence is better for the top-end people, and for the average Joe, surely you agree that they would benefit from more intelligence. So, objectively, more intelligence is currently better for everyone.
I'll assume you agree that being physically more attractive is desirable, given that you didn't address it.
Anyway, my overall point is that most people can agree that having certain traits or better traits is desirable, and your 'everything is subjective' spin isn't congruent with reality. Therefore, it remains possible to select for positive human traits (e.g. higher I.Q.), and then determine which race of humans are genetically better than others.