Sure; you can argue that races don't exist, if you want to be a sophist about it.
Like colours, or species, they're just a sociocultural construct; ad hoc buckets we use to classify into separate categories something that's really more of a continuous multidimensional gradient.
But.
Unlike races, racism does objectively, undeniably exist. Racists exist, and they discriminate, and cause all forms of harm and violence upon the people they discriminate against.
It's entirely irrelevant whether the buckets they use to fit their victims in have any actual existence outside their rotten little brains or not (in fact the fact that races don't really exist should only make their irrational discrimination even more unacceptable, if anything; and dangerous: you never know when they might decide to change their bucket so that you fit in it).
Racists will discriminate. They'll cause harm. They'll cause violence. That will happen, regardless of the actual existence or lack thereof of the races they discriminate against.
And, as long as there's racism, there'll be victims of racism.
So, again, sure, don't acknowledge races if you don't want to.
But you should absolutely acknowledge racism and its victims (and take into account racist's lunacies, such as races), since those are 100% real, and even if you currently fit into their "good" bucket, they will affect you, and the people you care about.
