A while back I had a similar discussion regarding my affinity for MLP. Like many, what caught and maintained my interest for the show went past that of the noticable break in the 'girls show' cookie cutter mould established by the previous generations, and the influence of the fanbase itself. To reiterate, here was my thoughts on the matter:
To me, as well as many others, My Little Pony: Friendship is Magic, is a welcome breath of fresh air to a stagnant market.
The series doesn't adhere to either male or female stereotypes, but instead settles itself in a mid-ground that has attracted such a diverse and varying fan-base that I never previously would have thought possible.
What really caught my attention to MLP:FIM, is that the show possesses some of the most unique and distinctive animation styles out there today, in comparison to other cartoons of similar nature. Take these screenshots for example.
While many animation series tend to recycle backgrounds to the point where they appear indistinctive, in almost every scene within the MLP series, there is a degree of variance; houses manage to appear analogous yet distinguishable in their own right, and add to the depth and beauty of each scene.
Sure, you could argue that I'm rambling about features that one doesn't necessarily focus on in a cartoon, but honestly, that's what most bronies love to do. We love to pick apart scenes right down to the tiny details, heck, even the animators of the show recognised this and regularly chuck in little easter eggs for our community to find!
All in all, Hasbro has brought a welcome and innovative change to the field of cartoon animation, and the fact that this came for the last franchise I would have ever imagined, makes it all the more commendable.
As for attempting to explain my fondness for the show (to those who can only perceive it from an entirely different perspective), I generally recommend that they watch a least an episode or two before listening to all of my reasonings; that way they can at least relate to what I'm trying to convey, granting me a bit more of a scope to work with.
All in all, trying to justify watching a show that the majority of society expects you to recoil to in inordinate horror to, is a tricky feat to say the least. However, with a bit of perseverance and guidance, in combination with a good measure of love and tolerance, it's possible to win over even the most ill-informed anti-brony.