EDIT: Bloodeagle ninja'd me. What follows was a response to 20%
Actually, while the intentional act of discriminating requires some level of intent, discrimination does not. You also appear to be in need of some self-education on implicit, casual, or systemic discrimination (all three terms cover essentially the same thing). For example, casual racism or casual misogyny do not require intent - my last post elaborates more on that subject.
Yours is the common argument of dilution - that racism can't be that bad if classism isn't that bad (because its common), which in turn isn't that bad if discrimination on another category which is not politically charged is even more common.. It's not applicable. (Also, your use of the term nationalism in the context you've stated is denotatively incorrect and adds no weight to your argument.) As I've said in past threads on this subject, humans cognitively function by creating in-groups and out-groups. The creation of those groups heuristically in cognitive process is not harmful; action or perpetuation of [ungrounded] negative stereotypes based on them is.
Furthermore, your use of phrases like "sandy vagina" and "delicate, flowery sensibilities" shows you have a poor grasp or irony, historical use of language, lack of self-awareness in how you write, or a combination of all three.
It's not about offending people. It's about some self-awareness of how social boundaries are created and enforced through the use of everyday language and the emphasis of negative stereotypes. Was the clerk intentionally racist? Unlikely, but there's a stack of evidence for implicit racism at work, just like I have no doubt that you did not intend for your earlier comment to be misogynistic, even though it absolutely was.