[sarasi]

No, the tattoo bans are very long-standing in Japan and were definitely implemented to keep out the yakuza. If they keep out members of other gangs then I'm sure the management is quite happy with that as a side-effect though. I wouldn't call the yakuza pussycats either, they still have a lot to do with the drug trade, intimidation and all kinds of fraud as well as still being involved in plenty of murders including the assassination of the mayor of Nagasaki not so many years back.

As for the question on what grounds do public swimming pools ban people with tattoos, well, on the grounds that the majority of their patrons are quite happy to see that ban in place. If the public thought that the ban was unreasonable and unfair, then it would have to be removed. Currently the public here does not think so, therefore the bans remain.