Respectfully, you are wrong. Those kanji are used in Japan to denote BJJ.
I get emails from my club using those kanji all the time. They write Brazilian in katakana (characters used for foreign words) and then use those kanji for ju jitsu. The people at my club are Japanese, they write in Japanese and they train BJJ.
http://www.office-fx.com/gracie/
This is my club's home page - you can see the characters used at the top of the page in white going from left to right. It says, Nagoya (3 kanji) Bu ra ji ri a nn (Brazilian - 6 katakana) Juu jutsu (the 2 kanji in question) then ku ra bu (club - 3 katakana)
Arguing over the name ju jitsu is such fun.
As for kanji tattoos, well, I can read kanji (at least to an extent) and I've seen all sorts of nonsense tattooed on people. If you want Ju Jitsu tattooed on you in kanji why not? At least it has some meaning. I'm not saying a flowy triangle wouldn't be cooler though.
PS katana - sword, katakana - type of alphabet