Dude, don't be sexist. The show has never been 'strictly girls only' and never been wimpy because the primary audience is girls. Girls can like fighting games, and many fighting games are geared towards children, such as this is. Fighting Is Magic is a totally kid friendly sort of battler with no blood or whatever- why would anyone object to children seeing that?
Also it's pretty well known that this show is loved by people of all ages, especially adult men. And Hasbro has repeatedly aknowledged the "brony" community and made it clear that they have no intention of making some big push to go "NO THIS IS ONLY FOR YOUNG GIRLS, YOU CAN'T WATCH". They've made loads of injokes and stuff specifically for the older audience, so I doubt they'd suddenly turn around and say 'oh noes, something that makes adults feel included! better nuke it!'
Also have you even watched the show? There is danger and fighting in it, what are you on about? How is fighting contrary to the 'message' when they commonly defeat big villains in epic showdowns of harmony laser beams?
Unless you mean specifically the fact that they're fighting EACH OTHER.. that is just total nonsense. Tie-in fighting games rarely have a plot, and without a plot noone is gonna look at the game and assume "OH NO THE MANE 6 ARE HURTING EACH OTHER OMG THEY'RE NOT FRIENDS ANYMORE". Noone rationalizes like that, they'd just think "oh look its a non canon totally plotless game where I can play as all the ponies".
There's been fighting games for TV shows before! There has NEVER been a news story about kids getting upset that the characters are fighting each other, or thinking it's equivelant to if they actually fought in 'real life'. Games are just imaginative play, the show is the actual canon- what happens in one isn't equal to the other. Sure, kids would probably be scarred forever if they were watching the show and Applejack suddenly started beating up Rarity, but who'd have a problem with some non-canon horsing about (pun not intended) where noone actually gets hurt and the only consequence of losing is losing some points?
If children took fighting games seriously then they'd freak out when they played a character against the same character, thinking there was some sort of evil plot to clone the mane cast!!1! Or in puzzle games they'd think that a bunch of bubbles or squares or whatever had suddenly fallen from the sky into Equestria and the ponies really were moving them around to make them dissappear, or else the world would be doomed. You gotta give kids more credit- they know the conventions of videogames
And a game convention for mascot fighters is "characters fight but noone gets hurt and nothing really happens". There's TONS of these things for all sorts of cute and harmless shows that don't normally have battles, and noone has EVER decided to cancel one because it's 'too scary for kids to see the characters fighting their friends' or whatever.. there's a friggin SPONGEBOB fighting game!
So yeah in summary: I think that is a terrible excuse and probably not what Hasbro's reasons were. I think they probably DID think "oh noes somehow this will mean less sales of the real videogames", even though I don't agree that that would actually happen.
Sorry if I'm being rude here