It forces people looking at it to ask questions regarding it and to have conversations. Just because it's your personal opinion that nothing will come out of it doesn't mean that's what is going to happen.
Also you mentioned people are culturally conservative in Tokyo, yet they have an odd definition of "conservative" which differs person to person. Last I checked the Akihabara distrcit is very much still a part of Tokyo :P.
Lastly how is a condom in any way offensive?
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Classic Zombergy, finding offense that goes against your delicate conservative sensibilities. The "rampant" STD problems statistic wise are more or less equal in heterosexual and homosexual people with some high numbers found in both.