I think it's funny that the fact ainu people don't look japanese despite indeed being japanese
what makes Ainu different from Japanese?
I didn't think the Ainu are accepted by Japanese because of their physical appearances
It is interesting to study these people, but it's not appropriate to joke about them when they are highly marginalized and shunned by society. You should be more respectful about traits they can't control, because every day they are isolated from the Japanese majority because of their ethnicity.
It's not like it's the end of the world
It's not the end of the world, but it can still be very hurtful toward them. You should work on respecting other cultures, not making fun of them.