Ah, Soul Eater. I watched the anime and read the manga about 2 years ago.
The manga is better than the anime, in my opinion. It's a fun series nonetheless.
There's better, though.
Thing is, aside from the creations of Rare and Retro Studios, pretty much all Nintendo characters are Japanese.
The only requested characters for Smash that aren't Japanese are Dixie Kong and King K. Rool.
I do agree that the anime fanbases are mostly insufferable, though I say the same about the Smash fanbase... Well, pretty much every fanbase, as a matter of fact.
The ******** about anime-like swordsman is still stupid, nonetheless. You can't even blame Sakurai for that.
It is a fact that Japan uses sword-wielding characters (especially heroes/protagonists) in pretty much everything. Even modern settings will often feature swordsmen for whatever reason. You know, rule of cool. They just like that stuff. Nothing wrong with that, I'd say. It's probably a cultural thing.
I mean, of the anime characters I showed earlier, half of them use a katana as their main weapon. You know, the main weapon of a samurai. Again, it's likely a cultural thing. Japanese feudalism lasted until late 19th century when the USA re-introduced fire arms in the country, so this kind of stuff is probably more ingrained in their culture. (The first time fire arms were introduced in Japan was around the 15th~16th centuries by European explorers, specifically Portuguese, but were banished in the 17th century. Just a historical tidbit.)
Even mecha anime often feature giant robots using swords, so sword wielding characters in Smash isn't surprising at all.