In my honest opinion, I would let them continue with their fandom here so long as the artwork is SFW and doesn't violate any of the Terms of Service established by Nintendo. Besides, if we really want people to tone down on the furry fandom art, we then have to do the same for anyone bringing up everything else that doesn't even have any relation to the game or Splatfest theme. Again, the constant Team Fortress 2 references on WiiU's Splatoon, the wave of Overwatch art where you see Reaper's Death Blossom as he says "DYE, DYE, DYE!," and oh god the memes!
However, politics is where I draw the line. I have seem some artwork posted with political intent and I just usually report those because politics is something I want AWAY from Splatoon. If I wanted to play a game that has politics in it I would just log back into Eve Online or browse through The Imperium News site to see what shenanigans Goonswarm is up to again.
1. The difference here is that the furry fandom literally has nothing to do with the game
at all. That's why people have such a huge issue with it. Games like TF2 or Overwatch, you can relate to them because they're shooters and Splatoon is in fact a shooter in that respect, so they fall under the same genre, so in a sense those games are Splatoon's 2nd and 3rd cousin. Where as the furry fandom, there really isn't a game that's been furry exclusive outside of say Ratchet & Clank/Sly Cooper. But even then, those game's are singleplayer and not multiplayer. OW and TF2 are both multiplayer shooter games. Children don't really need to ask their parents "What's a furry?" Only to get some obscure look from their parental unit. A quick google search, only to find something NSFW that was drawn up, and honestly start to question what goes on behind Splatoon's closed doors. It's how lawsuits happen. But then again ESRB has no control over Online gaming, so there's the gray area. However we haven't reached that bridge and I pray to Callie & Marie that never happens.
2. Also Reaper's Ultimate, when someone was doing the whole "Dye dye dye." thing it's in relation to the Inkling's weapon, which is in fact ink/dye. So it pays homage to the series in some way. Splatfest being a hard gray area, since you are representing a team in a sense, then by all means go ahead and draw whatever, but when you're purposely provoking the community by trying to get artist into the hivemind mentality that "We have freedom of expression." and try to draw people into a foreign culture (furry fandom in this case) with no relation to the game what so ever, then it's problematic. The issue I have is with artist purposely provoking others into driving a wedge into the community. Also it's on the furry community to moderate their behavior because calling someone a "Normie" because we dont' see your way of thinking
is not okay. It's just trying to rub salt in the wound when players obviously don't like it to begin with, so there's that.
As for politics, I keep away from them. Sure we have Splatfest which uses a vote system, but it's not really political. However what's really driving a rift between the Splatoon community on a more hidden/underground basis is the fandom between Marina and Pearl. People saying that Marina is nothing but fanservice or Pearl is nothing but an ugly spoiled looking brat due to having the crown on her head, when in reality, they're just polygons on the screen. I doubt your emotions will be conveyed to them further by trying to make mock up pictures of them in-game, displaying your distaste for either character. It's a game. Just play what you like, like whoever you like and keep it at that. If someone disagrees with you, then agree to disagree and leave it at that.