But this is a poster for a World Tour. A poster that will be used, likely, as the branding for his tour in all the countries he will visit.
I don't even actually care much about the 88 thing because, yes, its obscure... (which as an aside is why actual NN's like using it, because when people call it out, they can say "oh it's just a number, whatever do you mean? 
"). I think that tha is a more an unfortunate coincidence when put along with the poster.
The poster itself, as a whole, is the problem here though. The argument that the Nazi's banned fraktur so it's not relevant is silly. 5 minutes online can find you plenty of NN's, boneheads and faschy bois using that font for their Nazi loving nonsense. The common layperson in countries sensitive to Nazi iconography would still find the font, used in certain contexts, on the nose.
The poster is clearly trying to evoke a certain look and feel, which is "40's Germanic Facist chic". The poster needs to be taken as a whole. The sum of it's parts. The font. The name. The red flag. Even the black and white silhouette with a silver detail on the collar. Each of those alone wouldn't amount to much at all. But combined, there's clearly an effort to evoke a certain feel.
And you mean to say no one in his entourage, or company, or design group or whichever international company is handling the tours worldwide steps looked at this poster and said "Hey... you know what? Theres a chance this might get misinterpreted".
BUT ALSO, those same group of people also had such an intimate knowledge of Early 19th Century Typography as used by Facist Dictatorships" to know that this font was "safe" to use because the Nazi's banned it.
Now again, I don't think at all G-Dragon meant any harm here. I don't think it's entirely unreasonable to think he might have tried evoke a Nazi-chic type look because he thinks it looks cool in a vacuum, removed from the meaning others might take from it. But I do find it hard to believe that no one else near him pointed anything out. I think someone should have known.