Seriously, it's a legacy from back when 4chan was only a weaboo anime board and it goes counter of /d/'s internal culture of being tolerant of eachothers' individual kinks.
Keep this Japanese only shit for /a/ and /h/.
Name:
Dr Anonymous, phD2007-10-23 8:20
I can agree on the same-shit pointer, "if I see that fucking zombie/my life with comics/melonfuck again" seems to be the Number 1 Quote you are most likely to hear a /d/eviant say! Although to give credit, Muscle Monday and BBW-Wednesday churns out new material every week with minimal reposts.
One of the main reasons why /d/ is strictly for hentai is very obvious - it's naturally going to be filled with weeaboos who want to see stuff more kinky than just two anime characters humping each other. It's quite sad to say, but to some people on /d/ coming across a random Western pic is like coming across a furry in the middle of a Thread-of-Win. Also, going back to the "more kinky" part - /h/ is full of such prudes that they even seem to find anal play disgusting, there is no way that /d/ and /h/ could probably ever combine!
Borderline cases: I can kinda see where you're coming from. People cause shitstorms over Woot but effectively his work is in Japanese style, same with L0cke occasionally and his Tilt Mode. Shitstorms over these two haven't been made for a while - I guess fans of their artwork took the hint.
If your campaign of sorts unfortunately fails, then /b/ and /co/ are just two places on 4chan where you can ask for Western art porno (actually, /co/ I'm not too sure on, they used to allow it). /r/ even works if you be specific, and if you use it at the right time of the day!