http://www.destructoid.com/hater-vandalizes-tecmo-koei-building-calls-games-sh-t--197433.phtml

"The remarks spraypainted on the building are remarkably bitter and hateful. Such messages include, "Die", "garbage", "Shit game", and one other phrase that is either "Divine retribution" or "Tenchu", which is the name of a ninja-based franchise made by From Software"

now the real question is: why isn't this happening more often with EA's buildings?

Far be it from me to suggest or endorse vandalism, but I believe the answer to your question is that it does happen, but it is covered up and the perpetrator is never seen again.

Because Japan isn't just a different country, it's almost like a different world. Dynasty Warriors is HUGE over there so if Koei made a duff one then it would face a serious fan backlash.