^basically it. i'm going to make a lot of words.
some people have worded it really well. i am too on the side of being put off by BD. when it comes to sexual things, i am completely terrified of horses and ponies. and i love horses. i have a collection of 20 Breyer's horses (and a wolf and cougar of their making as well), and i love them, i've collected since i was a kid, and i still kind of want a horse. the exact reason i am terrified of horses/ponies sexually is because of bronies and now i can only withstand so much talk of MLP even casually. so you can see why this has hit a bad vibe.
Chance and Mary still held the same reaction because they're horses. but i could hold up a little better, as they were kinda just that. with this Sugar Star, it's /obviously/ MLP and, as others have said, a cash grab at bronies.
as another user has said it, it's that their ages while not disclosed is likely under. they are at a point they're old enough to not be totally dependent on their parents (as in not stay at home 24/7 like a child child) but not too old to be out of 'school'. they still have the a-moral-a-day kinda thing- which points that they're still /young/ and learning generally-basic topics. they are in the demographic of grade schoolers, and the easiest way to get them to relate is set in the same age group. so you can kinda see where this argument has a point.
in my personal opinion, BD could have done a lot better with Sugar Star. mostly it is the art (to me, her stuff just looks like... it was slapped on. i mean, does a vulva really stick off like that?). everyone kinda knows that Nox is a bit of a point at a Night Fury- but his art (while similar) is not immediately recognizable. a different color, has horns, spikes are different, no fins behind the wings, can't see if he's got a tailtip fin, i believe the wings are different too. i have a Nox in Night Drake and didn't really make that connection till after i got it. now when you look at Sugar Star, BANG. that's MLP, no doubts and instantly recognizable to people who even passively know the show (ie; have kids that watch it in the mornings before school). also on the topic of the art; it is also said that Sugar Star does not look 'adult'. taking from the artistic standpoint, there's an easy difference to child drawings to adults: children are drawn with mostly curves and rounded areas whereas adults are more straight lines and harsher angles, also longer limbs in relation to body size. baby anything has a larger head proportionally to its adult form. it's stated that SS has no connection to MLP however the art is style and all MLP hands down, so likely exists in the same place as the show.
people argue back in saying other shows that aren't so taboo to be into 'the' fandom; I'm going to use Transformers and HTTYD for this. both shows have demographics that are aimed at both kids and adults. this is easily told; Transformers is VERY complicated at times, and does have a lot of underlying subplot that children miss (you know kid's shows that had innuendos you totally missed when you were young?) while adults will catch, but the story while intense (the last movie, one of the first things was Ratchet being killed!) is easy enough for younger at face, and the action is incredible. plus, all the characters are adults (the Cybertronians are all millions of years old across all movies! *nerd moment*). for HTTYD; the characters are teens and now (as of HTTYD2) adults, likely in their 20's at this point. it's a short connection that Toothless as well is probably about the same age. in addition we have the movie plot; dragon's arent as bad as everyone thought, and in the second they need to save the dragons from Drago. but we also have Hiccup and Astrid's relationship, which kids really see a sappy love thing and don't pay much attention to it. we also have Stoic and Valka reunited, which kids see a happy thing but still don't see it as much as adults do. and also we have Stoic's death shortly after his reuniting with Valka. we also have the death of Valka's Bewilderbeast, then the completely charged scene of Drago's Bewilderbeast being defeated. again, it's action that intense but kids can follow and adults can enjoy.
TL;DR
BD could have done a lot better, and a lot better is mostly just getting different art for Sugar Star that wasn't so obviously MLP. people might not be in such a tizzy if, perhaps, she looked like she existed in the same world as Tucker and Chance.
also the backgrounds have put people off because it looks childish, which i agree and i've adbocked the two images. it's also said that the rotating backgrounds have been murdering mobile users' phones/etc., and for laptop people (like me) it make their computer auto change its brightness (as it rotates between 'light' and 'dark' images).
TOTALLY NOT ON THE TOPIC I WROTE A TON FOR
BD has lagged with toy drops but they've caught up a little and seem to have released a bunch of flops. also they are now going ot send lube sample packs with every order evidently, wonder how much is in them.
don't take mt saying BD as the entire company. i'm sure that the person who is simply pouring isn't to any blame. i commend their jobs, actually! but it's those in high power who haven't been thinking better (did they not think they'd get a ton of backlash for using that image for SS? (the artist did *okay*)).
though i do commend their customer service as well; they do a good job of being timely with their tickets and being fair with fixes. i had a lube bottle leak in my last order so they sent a new one free of charge.
also just a nitpick: Chance. two parts; one, his head. like, above the shoulders. it looks like a totally different art style from the body. like its a cutout or something! also with his other head... if you look between the flared and unflared you can see that the head just had the bubble tool used on it, and actually doesn't look like a flared head at all.
however until BD kinda fesses up or gets into better favor, i might be getting the toy i've wanted for my boyfriend (an anthro shark, Lily, or 'ess muzzle (in colors like Icestar on the last two) off secondhand and cleaning it REALLY good than i'd want to order from them. maybe a flop. maybe.