It is racism (or sexism, but we'll stick with racism for the sake of rhetoric and the article) though. Calling it "not racism" is pandering to white fragility because people think of themselves as "not racist". Calling it "not racism" gives people an out to not confront their own internalized racism.
It's humiliating for the "victim" because this probably happens on a daily basis. Tell me that wouldn't kneecap your confidence to constantly have to correct people and massage their egos and reassure them you're not offended just so they give you money. It's forcing the victim to perform the emotional labor of remediating the offense. It's wrong and we let people off the hook far too easily for it.
Those "associative generalizations" are racism, sexism and homophobia in a nutshell. You (not you in particular, but yeah, kind of) have certain associations bound to race. Acknowledge it, confront those feelings, and deal with them. It's your problem, not theirs; yet we constantly give people a pass on their own internalized racism because the people who are systemically oppressed by said racism aren't really in a position to call them out.
I'm not saying you should be fired from your job or anything; just that you should acknowledge that your generalizations do harm to people. Educate yourself on the things they go through to build empathy. Don't make them do the work you should be doing yourself. And don't assume that because they're exhausted from dealing with this daily and so don't act offended that they're not harmed by it.
The anti-racism movement is about white people not giving other white people a pass for casual racism. We have forced marginalized people of color to do the work on this front for too long, when it's a problem within the white community. Expect to be called out aggressively on this stuff from here on out until you educate yourself on why it's harmful.