Why would a guy claim to be blonde, when only women can be blonde?

@HumanEarth No, your brother is BLOND. NO "E". BLOND is MALE ONLY. BLONDE is FEMALE ONLY. THE TWO ARE NOT GENDER-NEUTRAL OR INTERCHANGEABLE. CAN'T YOU SEE THAT?

I never heard of such thing

Oh my, you're right

More about "Blond" and "Blonde"
If you're using "blond" as an adjective , you cannot go wrong because the adjective "blond" is used for everything. However, if you know the person is female, you can use "blonde" as an adjective to showcase your writing skills.

The same is not true if you're using "blond" as a noun. If the person is female, you must use "blonde" (or "blondes" for the plural). If you're unsure of the gender (e.g., "the teacher," "all the teachers") or it's a mixed group ("all the team members"), then use "blond" or "blonds

@HumanEarth I've never heard of the two being gender-neutral or interchangeable. Why do you think there are two different spellings? Didn't you pay attention to your French teacher when you were about 11 or 12?

@HumanEarth How did you get your "Oh my, you're right" comment to appear before mine? It wasn't there when I posted my comment. How do you do that?

Never took French

I posted a split second before you did

@HumanEarth We all did it between ages 11 and 13, it was (and I believe still is) part of the curriculum. We took our options at 13. I chose to take French, but not everybody did.

@KarenisKenziesmum This was not a common teaching in American schools. You need to address the audience you are asking if you are expecting regional or cultural answers.

@nonsensiclesnail I haven't been to America but I've been told they do French there.

@KarenisKenziesmum In high school, and for a very very small portion of the population it comes earlier, and specifically French. Not French in how it applies to American grammar.

@KarenisKenziesmum Yes we do French in southern parts of USA

Mostly German, Polish and Russian is common in Midwest and upper west coast

@nonsensiclesnail It has nothing to do with American grammar. French words always conform to French grammar regardless of what country someone lives in.

@KarenisKenziesmum And Americans follow American grammar rules, which are carefully picked and chosen, thrown into a blender and used in a willy nilly like fashion.

@nonsensiclesnail I'm sorry, but I cannot accept that. Everything has to be specific if it is to make sense.