And how was he racist? By being uncivil.
It doesn't matter if someone sits there thinking racist thoughts in their heads but doing nothing. What matters is actions. And the action in question was just incivility. The alleged motive is racism, but why would the motive even matter if the action itself weren't a problem?
These are not separate categories, they are overlapping ones, obviously. Lynching is racism, but it's also violence, not incivility. Saying the n-word is racism and uncivil. Other forms of incivility may not be racist. For the purposes of this sub-discussion, it doesn't matter if Trump was also racist, it was still incivility. It wasn't violence, for example.
So complaints about what Trump said are still just complaints about incivility, whether or not the motive behind that incivility is racism, and whether or not your motive for complaining about that incivility is because of racism.
And because you'll likely misunderstand this if I don't make it explicit, note that I'm not even saying it's wrong to complain about incivility. I'm not even claiming that it's wrong to have a special interest in racist incivility in particular. But the claim was made, and not by me, that if you're arguing about incivility then you've conceded the "actual case", whatever that may be. I'm merely pointing out the implication of such a position. Feel free to not agree about incivility being irrelevant.